U.  S.  DEPARTMENT   OF   AGRICULTURE, 

DIVISION  OF  ENTOMOLOGY— BULLETIN  No.  42. 

L.  U.  HOWARD,  Chief  of  Division. 


SOME  INSECTS  ATTACKING  THE  STEMS  OF  GROWING  WHEAT, 
RYE,  BARLEY,  AND  OATS, 


METHODS  OF  PREVENTION  AND  SUPPRESSION. 


PREPARED  UNDER  THE  DIRECTION  OP  THE  ENTOMOLOGIST, 

BY 

K.    M.   WEBSTER,   M.  S., 
Special  F^eld  Agent. 


WASHINGTON  \ 

GOVERNMENT     PRINTING     OFFICE. 
1903. 


U.  S.  DEPARTMENT   OF    AGRICULTURE, 
DIVISION  OF  ENTOMOLOGY— BULLETIN  No.  42. 

L.  O.  HOWARD,  CHIEl  of  Division. 


SOME  INSECTS  ATTACKING  THE  STEMS  OF  GROWING  WHEAT, 
RYE,  BARLEY,  AND  OATS, 


METHODS  OF  PREVENTION  AND  SUPPRESSION. 


PREPARED  UNDER  THE  DIRECTION  OF  THE  ENTOMOLOGIST, 

BY 

F\    IVT.  WEBSTER,   M.  S., 

Special  Field  Agent. 


WASHINGTON: 

GOVERNMENT     PRINTING     OFFICE, 
I903. 


LETTER  OF  TRANSMITTAL. 


United  States  Department  of  Agriculture, 

Division  of  Entomology, 
Washington,  D.  O. ,  September  £5,  1903. 
Sir:  I  have  the  honor  to  transmit  herewith  the  manuscript  of  a 
paper  entitled  ' '  Some  insects  attacking  the  stems  of  growing  wheat, 
rye,  barley,  and  oats,"  prepared  under  my  direction  b}^  Prof.  Francis 
M.  Webster,  temporary  field  agent  of  the  Division  of  Entomology, 
and  now  stationed  at  Urbana,  111.  Professor  Webster  has  acted  as 
field  agent  of  this  Division,  having  received  temporary  appointment 
since  1884,  with  headquarters  at  the  experiment  stations  of  Indiana, 
Ohio,  and  Illinois,  and  is  ably  qualified  for  the  prosecution  of  the 
present  work  through  years  of  study  in  the  States  mentioned  of  the 
insects  which  will  be  treated.  As  remarked  in  the  introduction,  this 
paper  deals  with  the  injuries  committed  to  small  grains  b}^  different 
forms  of  minute  flies,  eight  species  in  all,  which  are  generally  confused 
by  the  average  farmer  with  the  Hessian  fly.  The  differences  between 
these  various  species  and  their  method  of  attack  in  comparison  with 
that  of  the  Hessian  fly  are  dul}T  pointed  out,  and  many  valuable  sug- 
gestions based  upon  an  intimate  knowledge  of  the  habits  of  these 
insects  are  made  for  the  mitigation  of  their  ravages.  In  most  instances 
losses  by  these  insects  could  be  prevented  by  the  simplest  of  farming 
practices,  as  set  forth  in  their  proper  place.  I  recommend  the  publi- 
cation of  this  report  as  Bulletin  No.  42  of  this  Division.  The  fifteen 
text  figures  are  necessary  for  the  purposes  of  illustration,  those  illus- 
trating plants  having  been  kindly  loaned  by  the  office  of  Agrostologist. 
Respectfully, 

L.  O.  Howard, 
Hon.  James  Wilson,  Entomologist  and  Chief . 

Secretary  of  Agriculture. 
2 


CONTENTS. 


Page. 

Introduction 7 

The  genus  Isosoma 9 

Dealing  with  the  destructive  species  outside  of  the  grain  iields 11 

The  greater  wheat  straw-worm  ( Isosoma  grande  Riley) 14 

Previous  record  of  the  insect 14 

Discovery  <  >f  the  summer  f<  trm 15 

Discovery  of  dimorphism  and  alternation  of  generations 16 

Riley's  name,  Isosoma  tritici,  invalid 17 

Life  history 17 

Oviposition  of  the  spring  form  {minutum ) 18 

Oviposition  of  the  summer  form  (grandi ) 19 

Description 21 

Adults  of  summer  form  ( Isosoma  grande  Riley) 21 

Larva,  pupa,  and  egg  of  summer  form 21 

Adults  of  spring  form  (  Tsosoma  minutum  I 21 

Larva  and  pupa  of  spring  form 21 

Natural  enemies 22 

Preventive  and  remedial  measures - 22 

Distribution 23 

The  joint  worm  {Isosouki  tritici  Fitch ) 23 

Previous  record  of  the  insect 24 

Life  history 26 

Distribution 26 

Description 27 

Adult  female 27 

Adult  male 27 

Natural  enemies 27 

Remedial  and  preventive  measures 28 

Difficulty  in  recognizing  the  species 28 

The  barley  straw-worm  (Isosoma  hordei  I  Iarns ) 29 

Previous  records  of  the  insect 29 

Life  history 31 

Effect  of  the  larvae  on  the  plant 31 

Description 32 

Adult  female 32 

Adult  male 32 

Natural  enemies 33 

Preventive  measures 33 

The  captive  Isosoma  (Isosohhi  captivum  How. ) 34 

Description 34 

Adult  female 34 

•                      Adult  male 35 

3 


The  genus  Isosoma — Continued.  Page. 

Webster's  Isosoma  (Isosoma  websteri  How. )  35 

Description  of  adult  female 36 

The  hairy-faced  Isosoma  (Isosoma  hirtifrons  How. ) 36 

Description  of  adult  female 37 

Isosoma  secale  Fitch 38 

Description 38 

Adult  female 38 

Adult  male 38 

Fitch's  Isosoma  (Isosoma  fitchii  How.) 39 

Description ., 39 

Adult  female 39 

Adult  male 1 39 

The  two- winged  grain  and  grass  flies ■_ 40 

Were  probably  originally  grass  feeders 41 

Early  reports  of  injuries  to  grain 42 

The  greater  wheat  stem-maggot  (Meromyza  americana  Fitch) 43 

Past  history  of  the  insect 43 

Life  history 46 

Description 47 

Adult  fly,  egg,  larva,  and  pupa 47 

Food  plants 47 

Selection  of  food  plants  by  the  adults 48 

Place  and  method  of  oviposition 48 

Method  and  nature  of  attack 49 

Extent  of  ravages 50 

Preventive  measures 50 

Natural  enemies ' 51 

The  lesser  wheat  stem-maggot  ( Oscinis  carbonaria  Loew) 51 

Life  history 52 

Food  plants 53 

Place  and  method  of  oviposition 53 

Nature  of  injury '. 53 

Extent  of  ravages 54 

Description  of  adult 54 

Close  resemblance  to  Oscinis  soror  Macq "     55 

Description  of  egg,  larva,  and  pupa 55 

Preventive  measures 56 

Natural  enemies 56 

The  American  frit-fly  ( Oscinis  soror  Macq. ) 57 

Confusion  with  other  species 57 

Depredations  in  Minnesota 58 

Life  history 59 

Food  plants 60 

Difficulties  in  studying  habits . 60 

Eemedial  and  preventive  measures 61 

Description 61 

Conclusion 62 


ILLUSTRATIONS. 


Page. 

Fig    1.  Canadian  rye  grass  (Elymus  canadensis) 12 

2.  Virginia  rye  grass  (Elym us  virgin irus) 13 

3.  Greater  wheat  straw- worm  (Isosoma  grande  Riley),  spring  generation, 

form  minutum;  stages 14 

4.  Greater  wheat  straw- worm  ( Isosoma  grande  Riley ) ,  adult  summer  form .  14 

5.  Head  of  wheat  partly  destroyed  by  Isosoma  minutum 18 

6.  Method  of  opposition  of  female  of  summer  form  (I.  grande);   b,  point 

in  straw  where  egg  is  placed 20 

7.  Pediculoides  ventricosus  Newp.,  a  mite  which  destroys  the  larva 22 

8.  Isosoma  tritici  Fitch ;  adult  of  the  joint  worm 24 

9.  Effect  of  joint  worm  in  wheat  straw 25 

10.  Isosoma  hordei  Harr. ;  adult  of  the  barley  straw-worm 30 

11 .  Isosoma  captivum  How. ;  adult 34 

12.  Isosoma  websteri  How. ;  adult  female 35 

13.  Isosoma  hirtifrpns  How. ;  adult  female 37 

14.  Greater  wheat  stem-maggot  (Meromgza  americana  Fitch);   stages  and 

effect  on  young  wheat  plant 44 

15.  Oscinis  soror  Macq.,  stages;  d,  head  of  Oscinis  carbonaria 52 

5 


SOME  INSECTS  ATTACKING  THE  STEMS  OF  GROWING 
WHEAT,  RYE,  BARLEY,  AND  OATS. 


INTRODUCTION. 

Throughout  the  United  States,  where  the  smaller  cereal  grains — 
wheat,  rye,  barley,  and  oats — are  to  any  considerable  extent  cultivated, 
a  multitude  of  injuries  to  growing  wheat  are  charged  by  the  average 
farmer  to  the  Hessian  fly;  whereas,  in  many  cases  these  ravages  are 
really  the  work  of  insects  whose  habits  differ  greatly  from  those  of 
that  insect.  Indeed,  some  of  them  are  not  flies  at  all,  and  even 
where  the  ravages  are  caused  by  flies,  these  ar'e  not  necessarily  the 
Hessian  fly,  and  the  same  remedial  and  preventive  measures  that  are 
applicable  to  this  notorious  wheat  pest  may  not  be  at  all  effective 
against  them.  In  fact,  it  is  with  the  hope  of  enabling  the  farmer,  as 
also  the  economic  student,  to  distinguish  between  some  of  the  chief 
insect  enemies  of  cereal  grains,  and  especially  between  many  of  them 
and  the  Hessian  fly,  that  this  publication  has  been  prepared. 

In  the  following  pages  the  author  has  restricted  himself  to  the  con- 
sideration of  two  groups  of  grain -affecting  insects,  the  one  composed 
of  true  flies,  and  the  other  not,  though  both  during  their  developmental 
stages  live  and  thrive  within  the  stems  of  wheat,  and  to  some  extent 
within  those  of  the  growing  grasses  as  well.  Indeed,  as  a  whole,  they 
were  doubtless  primarily  grass  feeders,  and  their  grain-attacking 
habits,  being  of  more  recent  origin,  brought  about  by  the  changed  con- 
ditions of  their  natural  food  supply,  consequent  upon  the  influences  of 
advancing  civilization,  may  be  looked  upon  as  a  modification % of  their 
original  methods  of  living. 

While  this  variety  of  food  plants,  including  the  wild  grasses,  as  well 
as  the  cultivated  grains,  probably  has  the  effect  of  more  generally 
diffusing  some  of  these  insects,  thus  rendering  serious  outbreaks  of 
less  frequent  occurrence,  the  other  phase  of  the  problem  is  that  though 
the  farmer  might  exterminate  them  from  his  fields,  they  would  still 
inhabit  the  grass  lands  and  from  there  continually  send  a  fresh  supply 
of  colonists  into  his  fields  to  repopulate  them.  But,  again,  this  has 
its  redeeming  features,  as  it  enables  the  grain  grower,  in  some  eases, 
to  meet  his  enemies  in  the  grasses  and  then1  tight  them  to  better 
advantage  to  himself  than  in  his  cultivated  fields.     The  Hessian  fly  is 

7 


8 

an  exception,  as  it  has  yet  to  be  found  attacking-  the  grasses  in  this 
country;  yet  several  insects  whose  injuries  in  the  wheat  fields  have 
been  charged  up  to  it  by  the  farmer  may  be  destroyed  to  a  greater  or 
less  extent  by  closely  pasturing  the  roadsides  and  fence  corners  in 
summer  or  burning  them  over  in  winter  or  early  spring. 

The  first  group  of  these  grain-attacking  insects  to  which  attention 
will  be  here  given  is  composed  of  those  that  are  not  flies  at  all  in  the 
true  sense  of  the  term,  but  small  ant-like  creatures,  realty  related  to  the 
ants  which  they  so  closely  resemble.  Their  }^oung  live  within  the  stems 
of  the  smaller  cereal  grains  and  grasses,  and,  though  these  rarety  kill 
the  wheat  stems  outright,  they  may  either  prevent  the  production  of 
th?  kernels  or  cause  these  last  to  shrink  and  shrivel,  thereby  greatly 
reducing  them  both  in  weight  and  market  value.  These  insects  are 
called  the  grain  and  grass  Isosomas,  and  their  young  are  the  wheat 
straw- worms  and  the  joint- worms.  What  is  still  more  surprising,  they 
belong  to  a  group  of  insects  the  majority  of  which  are  not  vegetable 
feeders,  but  parasitic  on  other  insects,  and  it  was  a  long  time  before 
entomologists  were  willing  to  accept  the  fact  that  they  were  the  real 
depredators  and  not  parasites.  This  doubt  as  to  the  real  food  habits 
of  these  insects  had  not  entirely  disappeared  up  to  1884,  when  the 
author  proved  by  successive  rearings  not  only  the  vegetal  habits  of  one 
of  the  species,  but  also  the  even  more  interesting  fact  of  dimorphism 
and  an  alternation  of  generations,  showing  that  what  appeared  to  be 
two  species  was  really  two  generations  of  one  of  them;  but  one  of  the 
generations,  being  wingless  in  the  adult  stage,  renders  it  the  more 
easily  controlled  by  the  farmer  through  a  rotation  of  crop.a 

The  second  group  of  insects  here  considered  is  composed  of  true 
flies,  and  these  also  are  both  grain  and  grass  feeders  in  the  larval  or 
maggot  stage.  All  true  flies  have  but  two  wings,  and  the  maggots 
have  no  jaws,  but  the  mouth  parts  consist  of  two  minute  hooks  whereby 
they  tear  or  slightly  wound  the  surface  of  the  tender  stems  and  suck 
the  juices  flowing  therefrom.  The  Hessian  fly  is  also  a  true  fly,  but 
its  form  partakes  more  of  that  of  the  mosquito,  while  these  under  con- 
sideration have  very  much  the  form  of  the  common  house  fly,  except 
that  they  are  smaller,  and  they  are  frequently  quite  differently  colored. 
The  maggot  of  the  Hessian  fly  is  larger  and  more  robust  than  are 
those  of  the  Oscinids,  though  shorter  and  differing  in  color  from  those 
of  Meromyza. 

Judging  from  my  own  experience  and  observation,  these  insects  are 
much  more  injurious  to  the  young  grain  plants.  One  brood  of  mag- 
gots of  Meromyza  work  in  the  full-grown  straw  it  is  true,  but,  as  a 
rule,  the  injury  at  that  time  is  seldom  very  severe,  while  the  larvae  of 
the  Oscinids  are  rarely  found  in  the  full-grown  straw,  except  in  the 

a  Reports  U.  S.  Comm.  Agr.,  1884,  pp.  383-387;  1885,  pp.  311-315;  1886,  pp.  573-574. 


9 

extreme  north,  notably  in  Minnesota,  and  in  Manitoba  and  the  North- 
west Territories  in  Canada.  The  Isosomas  do  not  attack  the  grain 
plants  in  the  fall,  and  thus  we  have  a  natural  division  between  the  two, 
which  is  applied  in  the  discussion  of  these  insects  in  the  following- 
pages. 

The  Oscinids  are  not  destructive  in  this  country  alone,  as  allied 
species  have  long  been  a  serious  pest  in  England,  France,  Germany, 
and  Sweden.  The  frit-fly  (Oscinisfrit  Linn.),  is  some  years  especially 
destructive  in  Europe.  The  gout-fly  (Chlorops  ta&iviopus  Meigen)  and 
the  wheat  bulb-fly  {Hylemyia  coarctata  Fallen)  are  both  more  or  less 
injurious  to  small-grain  crops  in  England.  • 

In  the  preparation  of  this  bulletin  the  writer  has  been  greatly  aided 
by  Dr.  Howard  and  his  corps  of  assistants,  both  in  the  Department  of 
Agriculture  and  also  in  the  United  States  National  Museum,  and  by  Dr. 
S.  A.  Forbes  in  kindly  and  promptly  placing  the  notes  and  collections 
of  the  Illinois  State  Laboratory  of  Natural  History  at  the  author's 
disposal.  The  writer  is  also  indebted  for  specimens  to  Dr.  James 
Fletcher,  entomologist  and  botanist  for  the  Dominion  of  Canada,  and 
for  similar  favors  received  from  Prof.  F.  L.  Washburn,  State  ento- 
mologist of  Minnesota. 

THE  GENUS  ISOSOMA. 

The  grass  and  grain  joint-worm  flies  belonging  to  this  genus  are 
widely  distributed  in  America,  some  of  the  most  important  ranging 
from  the  Atlantic  to  the  Pacific  coasts  and  from  Canada  southward 
probably  as  far  as  the  grains,  wheat,  rye,  and  barle}^  are  grown. 

The  genus  Isosoma  is  known  to  inhabit  Europe,  Africa,  Madeira, 
St.  Vincent,  Australia,  and  Tasmania.  In  Europe  it  ranges  over 
Russia,  Switzerland,  Germany,  Austria,  and  Italy.  When  the  insect 
faunas  of  Asia  and  Central  and  South  America  come  to  be  better 
understood,  we  shall  in  all  probability  find  that  species  occur  in  those 
countries  also. 

These  insects  belong  to  the  Chalcididse,  a  family  of  parasites  whose 
normal  food  is  other  insects  in  one  or  more  stages  of  their  develop- 
ment. For  a  long  time  entomologists  refused  to  believe  that  the 
species  of  Isosoma  and  their  allies  were  exceptions  to  this  supposed 
rule,  and  Harris  firmly  believed  that  Isosoma  hordei  was  a  parasite 
and  not  the  true  depredator  in  barley  straw.  Dr.  Asa  Fitch  after- 
wards established  the  fact  of  phytophagic  habits  in  /.  hordei  as  well 
as  in  several  other  species,  but  English  and  European  entomologists 
were  not  wholly  convinced,  at  least  not  all  of  them,  up  to  as  late  as 
1882.  When  the  writer  began  the  study  of  grain-infesting  Isosoma 
in  1884,  comparatively  little  was  known  of  the  habits  of  some  of  our 
most  common  species,  and  the  establishing  of  the  fact  of  dimorphism 

3G80— No.  42—05 2 


10 

and  alternation  of  generations  by  him  in  the  case  of  Isosoma  tritici 
Riley,  as  it  was  then  known,  and  I.  grande  was  without  a  parallel,  in 
this  genus,  and  so  remains  in  this  country.  Among  the  ten  or  twelve 
American  species  that  I  have  reared,  none  of  the  others,  so  far  as  I 
have  been  able  to  determine,  enter  the  pupal  stage  in  the  fall  and 
winter  in  that  condition^  and  thus  the  greater  wheat  straw-worm  {Iso- 
soma grande)  is  one  stage  in  advance  of  the  others  in  spring,  and 
the  spring  form,  minuta,  is  developed  at  the  time  when  other  species 
are  entering  the  pupal  stage.  This  is  also  the  only  species  that  I  have 
not  succeeded  in  rearing  from  food  plants  other  than  wheat,  with  the 
j^>ssible  exception  of  Isosoma  websteri,  which  might  have  been  reared 
from  young  cheat  plants,  though  I  hardly  think  this  probable.  The 
fact  that  I  have  only  found  this  latter  species  in  spring,  and  then  only 
females,  is  indicative  of  a  dimorphism  and  alternation  of  generations; 
but  unless  it  be  an  undescribed  species  reared  from  stems  of  Tricusjpis 
sesleroides,  which  is  very  late  to  mature,  being  even  later  than  any 
other  species  known  to  me,  I  do  not  think  such  alternation  can  be 
connected  with  any  other  species  that  I  have  studied.  On  the  othei 
hand,  and  at  the  other  extreme  in  the  matter  of  food  plants,  the 
Elymus  Isosoma  {I  elymi  French),  has  never  been  with  certainty 
reared  from  wheat,  though  abundantly  from  the  stems  of  cheat  grow- 
ing among  wheat  and  from  Elymus  growing  along  the  margins  of 
wheat  fields. 

I  also  find,  much  to  my  surprise,  that  I  have  reared  Fitch's  Isosoma 
tritici  aside  from  its  known  food  plant,  wheat,  only  from  Elymus  vir- 
ginicus.  Even  where  this  latter  grass  and  the  closely  allied  E.  cana- 
densis have  grown  side  by  side,  the  joint  worm  {Isosoma  tritici 
Fitch)  has  held  strictly  to  the  former.  The  white-spotted  Isosoma 
{I  albomaadata  Ashmead),  perhaps  the  most  closely  allied  to  7.  grande 
of  any  of  the  species  known  to  me,  and  which  we  should  suppose 
would  more  than  any  other  incline  to  dimorphism  and  alternation  of 
generations,  seems,  however,  to  show  no  such  tendency,  and,  more- 
over, I  have  reared  it  from  both  cheat  and  Elymus  virginicus,  the  life 
cycle,  so  far  as  I  have  been  able  to  follow  it,  being  parallel  with  those 
of  Isosoma  elymi,  I.  tritici,  and  I.  hordei.  I  do  not,  of  course,  wish 
to  obscure  the  possibility  of  an  alternation  of  generations  among  these 
insects,  with  a  different  food  plant  for  each  generation.  On  the 
opposite  page  is  given  in  tabulated  form  the  food  plants  of  the  spe- 
cies of  Isosoma  known  to  attack  grains  and  grasses  in  North  America. 

.  «  Should  the  observations  of  Dr.  Andrew  Nichols,  given  under  Isosoma  hordei, 
prove  correct,  this  may  in  future  prove  erroneous  as  to  I.  grande,  unless  the  latter 
also  attacks  barley. — F.  M.  W. 


11 


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1 

DEALING  WITH  THE  DESTRUCTIVE  SPECIES  OUTSIDE  OF  THE 

GRAIN  FIELDS. 

In  attempting  to  control  the  grain-infesting  Isosoma,  the  practical 
farmer  will,  in  several  ways,  find  himself  at  a  disadvantage.  The 
very  deceptive  resemblance  of  these  insects  to  ants,  and  also  to  others 
actually  beneficial,  will  prevent  his  readily  recognizing  them  in  the 
fields,  even  if  he  were  to  see  them  at  all,  and  it  is  only  when,  by  acci- 
dent, perhaps,  that  he  finds  the  worms  in  the  stems  of  his  grain,  that 
he  will  ordinarily  be  able  to  detect  their  presence.  As  the  develop- 
ment of  the  insect  takes  place  entirely  within  the  straw,  rarely, 
except  in  the  case  of  two  species,  showing  any  external  effects,  much 
injury  may  occur  to  the  kernels  of  grain  without  his  being  able  to 
determine  the  cause.  It  is,  therefore,  advantageous  to  him  to  know 
that  he  ma}^  reduce  the  chances  of  injury  by  careful  attention  to  the 
uncultivated  areas  that  inevitably  surround  his  cultivated  fields.  As 
an  illustration  of  the  influence  of  neglecting  uncultivated  patches  like 
fence  corners  and  roadsides,  and  allowing  these  to  become  overgrown 
with  the  different  species  of  rye  grass  (Elymus),  I  give  the  results  of 
my  own  rearings  of  these  insects  from  stems  of  grasses,  taken  from  two 
different  localities  along  the  Illinois  Central  Railway.  In  connection 
with  what  is  here  given,  it  might  be  well  to  call  attention  to  the  fact 
that  the  grounds  within  the  fences  along  our  more  important  railways 
are  usually  better  kept  than  are  similar  uncultivated  grounds  along 
the  highways,  to  say  nothing  of  the  fence  corners,  borders  of  open 
ditches,  and  similar  tracts  on  the  premises  of  the  farmers  themselves. 

The  locality  from  which  I  secured  the  greatest  number  of  barley 
straw- worm  flies  {Isosoma  horde i)  is  situated  about  2  miles  north  of 
Champaign,  111.  The  contour  of  the  ground  is  such  that  mowing  over 
in  summer  is  difficult,  and  burning  over  in  winter,  though  practical, 
probably  did  not  seem  necessary  to  the  railwa}'  people.  As  a  conse- 
quence, a  small  tract  grew  up  to  the  Canadian  rye  grass  (Elymus 


12 


canadensis,  fig.  1),  the  stems  of  which  literally  swarmed  with  the  larvae 
of  this  species.  It  beyond  question  would  have  furnished  enough 
adults  to  have  stocked  hundreds  of  acres  of  barley  had  it  been  within 
reach.  The  presence  of  the  old  stems  clearly  indicated  that  the  place 
had  been  neglected  for  years,  and  grass  stems  of  the  previous  year 
were  filled  with  punctures  where  the  adults  had  made  their  escape. 
Without  anyone  knowing  it,  there  was  here  kept  a  perpetual  nursery 
for  barley  straw- worm  flies,  and  though  not  at  present  a  barley  coun- 
try, it  is  true,  it  is  easy  to  see  what  the  effects  would  be  were  the  sit- 
uation otherwise  and  must  be  elsewhere  where  this  grain  is  more 
largely  grown. 
The  locality  from  which  I  secured  the  least  number  of  these  insects, 
and,  in  fact,  none  of  the  grain-attacking  species 
at  all,  is  located  along  the  same  railway,  in  the 
edge  of  the  village  of  Peotone,  111.  Here  the 
topography  of  the  ground  along  the  railway  is 
even  worse  than  that  in  the  Champaign  locality, 
but  close  proximity  to  the  village  rendered  more 
attention  to  it  necessary.  I  am  informed  by 
those  living  near  the  place  that  it  is  regularly 
mown  off  during  the  latter  part  of  June  and 
again  in  September.  The  material  used  in  my 
breeding  experiments  was  collected  August  12 
at  Champaign  and  August  21  at  Peotone,  and, 
though  the  Canadian  rye  grass  was  much  more 
abundant  in  the  latter  locality,  and  to  all  out- 
ward appearances  at  the  time  the  material  was 
secured  offered  the  joint- worms  a  far  superior 
place  to  develop  there,  yet  with  ample  material 
I  did  not  obtain  a  single  individual,  though  in 
Dekalb  County,  about  60  miles  west  of  Chicago, 
where,  to  my  certain  knowledge,  no  wheat  or 
barley  has  been  sown  for  years,  from  grass  col- 

Fig.  1.— Canadian  rye   grass  J  *i  .  .  , 

(Eiymus  canadensis),  (after  lected  August  20  I  reared  quite  a  number  or 
Scribner)-  these  insects.     The  Dekalb  County  material  was 

collected  from  along  the  neglected  roadsides  in  the  country.  I  can 
see  no  possible  explanation  of  the  difference  in  abundance  of  the  joint- 
worms  in  the  rye  grass  secured  at  Champaign  and  that  secured  at 
Peotone,  except  the  difference  in  the  attention  given  to  mowing  off 
the  grass  during  the  summer — the  same  attention  that  farmers  can 
without  troubJe  give  to  the  roadsides,  fence  corners,  and  ditch  bor- 
ders on  and  about  their  own  premises.  These  things  are  a  part  of 
good  husbandry,  yet  among  intelligent  farmers  I  have  found  the  two 
species  of  rye  grass  growing  not  only  by  the  roadsides,  but  along  the 
very  borders  of  their  wheat  fields,  in  some  cases  the  grass  and  wheat 
being  intermixed  along  the  extreme  edges  of  the  fields  of  grain. 


13 


Under  much  the  same  conditions  I  heave  reared  the  greatest  numbers 
of  joint-worm  Hies,  at  present  known  as  Tsosoma  tritici  Fitch,  from*  the 
Virginia  rye  grass  (El/ymus  virginicus,  tig.  2).  In  this  case  the  grass 
from  which  I  secured  these  insects  in  greatest  profusion  came  from 
the  most  neglected  roadsides.  In  the  vicinity  of  the  city  of  Urbana, 
111.,  I  secured  material  from  two  localities,  one  quite  near  the  resident 
quarter,  where  the  city  government  required  the  mowing  off  of  weeds 
and  grasses,  commencing  in  June,  and  the  other  farther  from  town, 
along  a  neglected  bank  where  the 
grass  was  allowed  to  grow  up  un- 
disturbed year  after  year.  From 
grass  stems  from  the  former  local- 
ity I  secured  almost  nothing,  while 
from  that  coming  from  the  latter 
locality  I  obtained  enough  to  show 
that  there  was  here  a  constant 
menace  to  the  wheat  fields  in  the 
neighborhood.  Now,  as  a  matter 
of  fact,  there  is  comparatively 
little  wheat  or  rye  grown  in  the 
neighborhood,  and  until  1  reared 
these  insects  from  the  wild  grasses 
I  could  not  account  for  their  sud- 
den appearance  in  the  wheat  and 
rye  fields,  observed  and  recorded 
in  former  years  by  Professor 
Forbes  and  his  assistants.  What 
has  proven  true  here  has  been 
shown  to  follow  similar  conditions 
elsewhere  in  both  Illinois  and 
Indiana.  That  is  to  say,  where 
farmers  have  allowed  these  grasses 
to  grow  up  about  their  farms  year 
after  year  under  the  impression 
that  they  were  not  worth  any  attention,  I  have  found  the  insects  in 
abundance,  and  also  find  that  despite  their  otherwise  good  farming, 
they  have  probably  suffered  more  or  less  from  the  attacks  of  the 
two  species  of  destructive  Isosoma  in  their  grain,  though  they  may 
not  have  observed  them  or  their  subtile  effects  on  the  kernels  of  the 
wheat  and  rye.  I  am  convinced  that  there  is  an  element  of  loss  here 
of  which  farmers  are  unaware  and  the  precise  effects  of  which  they 
do  not  therefore  comprehend,  yet  might  if  they  realized  the  situation. 


Fig.  2.- 


Virg-inia  rye  grass   (Elymus    virginicus) 
(after  Scribner) . 


14 


THE  GREATER  WHEAT  STRAW- WORM. 

(Isosoma  grande  Riley.     Fig.  3,  form  minuta;  fig.  4,  form  grande.) 
PREVIOUS    RECORD    OF    THE    INSECT. 

The  history  of  this  species  extends  back  only  to  1880,  though  it  was 
probably  for  many  years  confused  in  wheat  with  the  joint- worm. 
It  sometimes  occurs  that  insects  which  the  sj^stematist  can  only  con- 
sider distinct  prove  on  thorough  study  to  belong  to  one  and  the  same 


Fig. 


-Greater  wheat  straw-worm  (Isosoma  grande  Riley),  spring  generation,  form  minutum:  a,  b, 
larva;  /,  female;  g,  fore-wing;  h,  hind- wing;  all  much  enlarged  (from  Riley). 


w 


species,  while,  on  the  other  hand,  it  sometimes  occurs  that  what  the 
systematic  entomologist  considers  the  same  species  prove  on  investi- 
gation to  be  entirety  different,  and  thus  the  problem  of  control,  if 
injurious,   is   either  simplified  or  complicated,  as  the  case  may  be. 

However  easy  it  may 
appear  to  the  farmer, 
to  learn  all  of  the  life 
history  of  an  insect  is 
not  unfrequently  a 
matter  of  no  little  dif- 
ficulty. Where  we  can 
follow  out  the  life  cycle 
of  a  species  accurately, 
there  is  usually  found 
some  place  or  period 
in  its  existence  when 
it  is  more  easily  con- 
trolled or  destroyed 
than  at  any  other  time, 
and  it  often  occurs  that 
at  the  critical  point  some  simple  manipulation  of  his  land  or  his  crop, 
on  the  part  of  the  farmer,  will  accomplish  wonders.  This  species 
seems  to  offer  illustrations  of  all  of  these  features. 


Fig.  4. — Greater  wheat  straw- worm  (Isosoma  grande  Riley) ,  adult 
summer  form,  much  enlarged  (from  Howard). 


15 

In  June,  1880,  Mr.  J.  K.  P.  Wallace,  of  Andersonville.  Tenn..  sent 
to  Dr.  C.  V.  Riley  a  number  of  wheat  straws  containing  larva',  with 
the  complaint  that  nearly  every  stalk  or  straw  was  affected  by  them, 
and,  as  a  consequence,  the  straw  was  inclined  to  fall  before  the  grain 
had  fully  ripened.  Mr.  J.  G.  Barlow,  of  Cadet,  Mo.,  about  this  time 
also  complained  of  a  similar  trouble  in  his  neighborhood,  in  sonic  cases 
resulting  in  nearly  a  total  loss  of  the  crop.  In  the  winter  of  LssL-82, 
Dr.  Riley  was  able  to  rear  some  30  adults  from  these  infested  straws, 
and,  as  he  considered  the  species  described  by  Dr.  Fitch  only  a  variety 
of  the  barle}T  straw-worm  (Isosoma  hordei  Harris),  he  described  the 
adults  obtained  from  these  straws  as  Ix<>s<>,n<i  trifle/  Riley,  which 
description  was  published  in  the  Rural  New  Yorker  March  1,  1882. 
This  was  the  situation  and  the  condition  of  our  knowledge  of  the 
species  at  the  time  the  writer  was  appointed  a  special  agent  of  the 
Division  of  Entomology,  of  which  Dr.  Riley  was  then  chief,  and 
under  his  instructions  began  the  study  of  these  and  other  grain  insects 
in  May,  1884. 

DISCOVERY    OF   THE    SUMMER   FORM. 

On  Ma}T  8,  1881,  in  a  field  of  wheat  near  Bloomington,  111.,  I  found 
Isosoma  tritiei  Riley,  as  it  was  at  that  time  known,  in  considerable 
numbers,  crawling  over  the  young  wheat  plants,  and  on  the  11th  of 
the  same  month  watched  a  couple  of  females  deposit  their  eggs  in  these 
growing  plants.  On  May  30,  while  examining  plants  from  this  same 
wheat  field,  }- oung  Isosoma  larvae  were  found  in  the  stems,  and  I  also 
found  larvae  in  the  stems  in  which  I  had  observed  the  captured  females 
to  oviposit  May  11,  but  these  last  were  much  too  large  for  Is<>x<>m<( 
tritiei.  During  the  previous  few  days  I  had  been  getting  from  fields 
of  both  wheat  and  rye  in  the  same  locality  a  much  larger  Isosoma, 
possessing  fully  developed  wings,  and  on  May  i>(.»  a  pupa,  also  too 
large  for  I.  tritiei,  was  found  in  the  upper  part  of  a  dwarfed  wheat 
plant.  In  the  light  of  more  recent  studies  we  now  know  that  I  had 
three  species  under  observation  instead  of  one.  The  small  individuals 
found  early  in  the  month  of  April  belonged  to  the  spring  form  of  this 
species,  and  others  were  Isosoma  websteri,  while  the  larger  individuals 
swept  from  wheat  and  rye,  later  in  the  month  of  May,  were  some 
of  them  the  summer  form  (L  grande),  and  others  belonged  to  another 
species,  afterwards  described  as  Isosoma  captivum  Howard.  My  field 
of  observation  was  at  this  time  transferred  from  Bloomington,  111.,  to 
Oxford,  Ind. 

On  June  6,  in  a  field  of  wheat  near  Oxford,  I  observed  female  Iso- 
somas,  seemingly  like  those  taken  a  few  days  before  in  the  wheat  and 
rye  fields  near  Bloomington,  ovipositing  in  wheat  plants,  well  up 
toward  the  top  of  the  stem,  probably  between  the  upper  joint  and  the 
one  next  below,  although,  on  account  of  the  head  of  the  wheat  having 
not  }Tet  put  forth,  it  seemed  as  though  the  egg  was  being  placed  in  the 


16 

upper  joint.  A  large  number  of  these  adult  females  were  secured,  and 
these  constituted  the  types  upon  which  the  description  of  Isosoma 
grande  was  based. a 

DISCOVERY    OF    DIMORPHISM   AND    ALTERNATION    OF    GENERATIONS. 

At  harvest  I  arranged  with  the  owner  of  the  field  near  Oxford  to 
allow  a  small  area  where  I  had  witnessed  the  oviposition  of  the  female 
Isosomas  to  remain  uncut,  and  I  afterwards  secured  these  straws,  apart 
being  kept  out  of  doors  and  the  remainder  kept  within  doors  during 
the  following  winter.  Some  conception  of  the  extent  to  which  these 
straws  were  tenanted  b}^  the  larvae  of  this  species  may  be  gained  by  the 
fact  that  of  90  straws  from  the  same  field  81  were  infested  and  con- 
tained 136  larvae.  These  straws  were  cut  close  to  the  ground,  and, 
therefore,  the  contained  larvae  represented  the  total  number.  Of  90 
straws  as  cut  b}^  the  harvester,  there  were  a  far  less  number  of  larvae 
present,  only  25  being  found  in  the  entire  lot,  the  remainder  having 
been  left  in  the  stubble. 

By  October  all  of  the  larvae  had  pupated,  and  my  first  adult  was 
obtained  December  7  from  the  lot  of  straws  kept  indoors.  From 
this  time  on  till  June  I  continued  to  secure  adults  issuing  from  these 
straws,  but  everyone  of  them  were  Isosoma  tritici  Riley.  All  of  the 
straws  were  now  split  open  in  order  to  determine  whether  or  not  any 
individuals  still  remained,  but  none  were  found. 

My  first  adult  from  the  straws  kept  out  of  doors  appeared  March 
23,  and  others  continued  to  appear  up  to  the  first  week  in  April,  all,  as 
with  the  straws  kept  indoors,  being  Isosoma  tritici  Rile}^.  These 
straws  were  now  split  open  and  examined,  but  there  was  no  trace  of 
Isosoma  grande,  which  I  knew  had  deposited  eggs  in  these  very  straws. 
Despite  all  this,  on  June  1,  in  sweeping  the  grass  along  the  borders 
of  a  wheat  field  at  Lafayette,  Ind. ,  only  about  20  miles  from  where 
I  had  found  them  the  previous  year,  1  captured  Isosoma  grande,  and 
on  the  following  day  found  them  present  in  the  wheat  fields. 

During  the  fall  of  1885  1  took  the  precaution  to  sow  a  small  plat  of 
wheat  and  so  protect  it  that  no  insects  could  reach  it.  The  cover  was 
renewed  in  spring,  and  some  of  the  Isosoma  tritici  emerging  from 
straws  taken  from  the  field  the  previous  summer  were  placed  in 
the  inclosure  where  the  young  protected  wheat  plants  were  grow- 
ing. The  adults  were  placed  on  this  young  wheat  April  12,  and  the 
utmost  care  taken  to  prevent  any  other  insects  from  reaching  them, 

a  The  records  and  material  in  the  files  and  collections  of  the  State  Laboratory  of 
Natural  History  show  that  what  is  probably  the  larvae  of  this  species  was  found  in 
abundance  in  wheat  straw  in  the  fields  in  southern  Illinois,  in  July,  1884,  and  adults 
of  the  summer  form  (grande)  were  collected  by  Mr.  Garman,  at  that  time  an  assistant 
of  Dr.  Forbes,  in  various  localities  in  southern  Illinois,  during  late  May  and  early 
June,  1884,  or  just  about  the  time  that  I  began  to  observe  it  about  Oxford,  Ind. 


17 

and,  besides,  the  fields  were  closely  watched  for  Tsosoma  grande.  On 
June  2,  fifty -one  days  after.  I  found  a  female  of  Isosoma  grand*  in  the 
inelosure  and  in  the  act  of  ovipositing  in  the  now  full-grown  wheat 
plants.  Others  were  observed  similarly  engaged  during  the  follow- 
ing fortnight,  and  when  the  straw  was  ripened  it  was  cut  oh1'  and 
placed  in  glass  jars.  I  had  thus  again  reared  the  one  supposed  species 
from  the  other.  During  the  following  winter  many  adults  were  reared 
from  these  straws,  but  all  were  of  the  one  form  (/.  tritiei  Riley),  and 
I  had  reared  the  two  forms  twice  from  each  other,  leaving  now  no 
further  doubt  that  they  were  simply  two  generations  of  the  same 
insect,  besides  showing  that  as  the  spring  generation  is  without  wings 
and  can  not  fly  from  one  field  to  another,  a  simple  rotation  of  crop  on 
the  part  of  farmers  would  result  in  keeping  the  insect  so  reduced  in 
numbers  as  to  place  it  out  of  necessary  consideration  as  a  wheat- 
destroying  insect. 

In  all  of  my  own  rearings  of  both  forms  of  this  species  I  did  not 
secure  a  single  male,  and  of  the  large  number  reared  at  the  Depart- 
ment of  Agriculture  at  Washington,  from  material  furnished  by  me, 
but  three  individuals  of  this  sex  were  obtained. " 

riley's  name,  isosoma  tritici.  invalid. 

In  a  more  recent  study  of  these  insects, b  Dr.  L.  O.  Howard  found 
that  the  species  described  by  Dr.  Fitch  as  Tsosoma  tritici  was  a  valid 
one.  This  being  the  case,  Riley's  name  must  no  longer  be  used,  and 
the  later  one,  Isosoma  grande,  thus  covers  both.  Doctor  Howard  has 
given  the  name  mi/nutum  to  the  wingless  spring  form,  and  this  name 
will  hereafter  be  used  in  this  paper. 

LIFE    HISTORY. 

The  insect  passes  the  winter  in  the  center  of  the  straw,  just  above 
the  joint,  in  the  pupal  stage.  Rarely  an  adult  will  emerge  in  late 
autumn,  but  if  kept  indoors  others  will  appear  during  December,  the 
most  during  January,  showing  that  they  are  ready  to  appear  during 
the  first  settled  warm  weather  in  spring.  In  further  proof  of  this,  I 
have  found  that  as  the  winter  advances  they  require  less  time  indoors 
in  which  to  develop  than  if  the  straws  are  brought  in  in  December, 
thus  showing  that,  while  subject  to  all  of  the  influences  of  winter,  they 
are  undergoing  a  change  that  carries  them  nearer  to  maturity.  With 
the  settled  spring  weather  they  eat  a  round  hole  in  the  straw  and 
make  their  way  forth.  As  males  are  few  they  rarely  pair,  if  at  all, 
but  are  ready  to  begin  oviposition  as  soon  as  out  of  the  straw.     They 

a  Report  U.  S.  Coram.  Agr.  1886,  p.  573,  footnote. 

&  Grass  and  Grain  Joint-worm  Flies  and  their  Allies,  Tech.  Ser.  2,  Div.  Ent., 
U.  S.  Dept.  Agr. 

3680— No.  42—05 3 


18 


Fig.  5. — Head  of  wheat  partially  de- 
stroyed by  Isosomaminutum  (drawn  in 
Division  of  Entomology). 


are,  except  in  rare  cases,  entirely  devoid 
of  wings,  and  migration  is  therefore  out 
of  the  question,  except  for  short  distances. 

oviposition    of    the    spring   form 
(mintjtum). 

At  the  time  that  the  minute,  wingless 
females  that  comprise  this  form  appear 
in  spring  the  young  wheat  plants  are  only 
starting  to  throw  the  stem  upward,  and 
if  one  will  take  the  trouble  to  cut  one  of 
them  directly  through  the  center,  longi- 
tudinally, he  will  be  able  to  observe  the 
embryo  head  not  far  above  the  surface 
of  the  ground.  Pushing  its  ovipositor 
through  the  stem  to  the  center,  the  mother 
insect  places  her  egg  in  the  embryo  head, 
which  is  not  only  the  most  vital  part  of 
the  plant,  so  far  as  the  f  ruitf ulness  thereof 
is  concerned,  but  where  her  offspring  will 
be  in  the  midst  of  the  most  tender  and 
highly  nutritious  food  possible.  As  a  re- 
sult of  this  the  young  head  is  destroyed 
and  further  growth  of  the  stem  prevented. 
In  some  instances  the  young  larva  is  itself 
destroy  ed  before  it  has  finished  its  destruc- 
tion of  the  head,  and  a  distorted  wheat 
head  supported  by  a  dwarfed  and  weakly 
stem  is  the  consequence.  One  of  these 
partly  destroyed  heads  is  illustrated  in 
fig.  5.  In  most  cases  the  stem  ceases  to 
grow,  withers  up,  and  dies,  though  usu- 
ally standing  upright,  at  the  height  of  from 
1  to. 6  inches,  with  the  leaves  drooping  down 
about  the  stem,  both  dead  and  discolored. 
In  feeding  on  the  young  head  the  larva 
forms  a  ceil-like  cavity  which,  owing  to 
the  size  of  the  larva  and  pupa,  sometimes 
takes  on  a  somewhat  gall-like  appearance, 
not  noticeable  except  when  cut  in  two.  It 
would  seem  that  the  superior  article  t)f 
food  which  nature  provides  for  these  lar- 
vae might  to  some  extent  account  for  the 
larger  and  more  robust  adults  which 
constitute  the  second  or  summer  brood. 
The  larvae  must  develop  quite  rapidly,  as, 


19 

by  June  10,  nearly  all  have  transformed  to  the  adult  summer  form 
{grcmde),  which  begins  to  appear  about  June  1 .  reaching  its  maximum 
in  point  of  numbers  about  June  20,  though  I  have  found  an  occasional 
individual  as  late  as  the  ^7th  of  that  month.  In  ovipositing,  minutwn 
seems  to  prefer  the  lateral  stems  in  which  to  place  her  eggs,  thus 
leaving  the  central  stem  unaffected.  With  the  summer  form  (grande) 
this  selection  is  reversed  and  the  largest  and  most  thrifty  stems  are 
selected.  Spots  of  rank  growing,  thinly  placed  grain  will  suffer  worse 
than  the  more  densely  growing  areas. 

OVIPOSITION    OF    THE    SUMMER    FORM    (GRANDE). 

Nurtured  in  the  midst  of  the  embryo  head,  we  would  naturally  look 
for  an  adult  insect  differing  somewhat  from  the  one  developing  from 
larvae  whose  food  is  of  a  coarser  and  tougher  nature,  and  in  this  case, 
whether  as  a  coincidence  or  otherwise,  we  have  a  much  larger  insect 
with  fully  developed  wings,  forming  in  consequence  the  migratory 
brood  of  the  species.  That  these  females  wander  about  from  field  to 
field  is  shown  by  the  fact  that  they  may  be  captured  during  June  by 
sweeping  over  the  grass  lands  with  an  ordinary  insect  net,  such  as  is 
used  by  entomologists  for  this  purpose. 

The  method  of  oviposition  between  the  spring  and  summer  forms 
does  not  differ  materially,  except  as  the  difference  in  the  conditions  of 
the  plant  makes  slight  variations  necessary.  The  former  must  place 
her  eggs  in  the  very  young  plant  comparatively  close  to  the  surface 
of  the  ground,  while  the  latter  seems  to  try  to  get  her  egg  immedi- 
ately above  the  uppermost  joint  of  the  wheat  stem  within  her  reach. 
At  the  season  of  the  }^ear  when  this  takes  place  the  upper,  and  fre- 
quently the  joint  next  below,  is  not  uncovered  by  the  leaves  and 
sheath,  but  the  majority  of  the  eggs  are  placed,  singly,  just  above 
either  the  second  or  third  joint  below  the  head,  and  rarely  above  the 
upper  joint.  The  significance  of  this  to  the  farmer  is  that  very  few  of 
the  larvae  hatching  from  these  eggs  will  be  taken  away  with  the  straw, 
but,  on  the  contrary,  left  in  the  field  in  the  stubble.  If  the  reverse 
were  the  case,  and  most  of  the  larva'  removed  with  the  straw  to  the 
barnyard,  there  to  be  either  run  through  the  stables  or  similarly  util- 
ized, in  most  cases  hardly  an  individual  would  get  back  into  the  wheat 
fields  in  spring,  for  it  must  be  remembered  that  at  this  period  the 
adults  are  wingless  and  incapable  of  flying.  The  method  of  oviposi- 
tion is  shown  in  fig.  6,  ".  and  the  point  where  the  egg  is  deposited  in 
the  straw  is  shown  in  figure  (3,  £,  the  transverse  line  showing  the  track 
of  the  ovipositor.  To  place  her  egg^  the  female  takes  up  her  position 
just  above  the  joint,  with  her  head  downward.  She  then  straightens 
her  legs,  thus  throwing  her  body  away  from  the  stem,  at  the  same 
time  bringing  her  feet  almost  directly  beneath  the  body.  She  now 
brings  the  abdomen  downward  and   forward  between  her  legs,  much 


20 


as  a  bee  would  do  if  alighting  and  instantly  stinging  an  animal.  The 
next  move  is  to  let  the  tip  of  the  abdomen  strike  the  stem  and  then 
go  back  to  its  proper  position,  but  the  tip  of  the  ovipositor  does  not; 
on  the  contrary,  it  catches  on  the  surface  of  the  stem,  directly  beneath 
the  body  of  the  insect,  and  by  putting  its  machinery  in  motion  and 
drawing  the  stem  toward  her  she  slowly  forces  the  ovipositor  into  the 
soft,  juicy  stem  at  the  point  where  this  is  solid  and  not  hollow,  as  is 
the  case  a  short  distance  above  and  immediately  below  the  joint.  The 
tip  of  the  ovipositor  is  composed  of  two  flattened  plates  arranged  side 
by  side,  the  edges  of  which  are  sharp,  and  are  propelled  with  a  sort  of 
rotary  motion  alternating  with  each  other.  In  this  way  the  ovipositor 
cuts  and  drills  its  way  to  the  center  of  the  stem,  and  an  egg  is  forced 
down  the  interior  and  left  in  its  proper  place  in  the  stem  of  the  plant. 
The  female  recovers  her  ovipositor  by  again  straightening  her  legs 

and  pushing  the  plant  from  her.  Only 
one  egg  is  placed  in  the  same  location, 
though  perhaps  more  than  one  is  placed 
in  the  same  straw  by  the  same  female, 
but  if  so  they  are  placed  above  different 
joints  in  the  straw.  The  larvae  must 
mature  quickly,  for,  though  pupation 
does  not  take  place  until  about  October, 
the  stem  ripens  and  becomes  tough  and 
woody,  wholly  unfit  for  the  food  of  the 
larvae,  within  less  than  a  month.  It 
would  seem  that  the  mother  insect  is 
aware  of  this,  as  she  invariably  selects 
the  greenest  and  rankest  growing  plants 
in  the  more  open  spots,  where  the  straw 
matures  the  slowest  and  remains  green 
and  juicy  the  longest. 
Briefly,  then,  the  insect  passes  the  winter  in  the  stubble — with  the 
exception  of  the  few  that  have  been  removed  with  the  straw — in  the 
pupal  stage.  In  late  March  or  during  April  the  spring  form 
(minutum),  small,  jet-black,  ant-like,  and  with  rare  exceptions  wing- 
less females,  eat  their  way  out  of  their  winter  home  and  seek  the 
young  growing  wheat  plants.  The}^  deposit  their  eggs  singly,  placing 
them  in  the  embryo  head.  These  hatch  within  a  few  days  and  the 
larvae  mature  and  transform  to  the  form  grande-,  large,  robust,  also 
jet-black,  with  fully  developed  wings,  in  late  May  and  the  first  two- 
thirds  of  June.  These  last  are  also  females,  and  without  pairing  they 
begin  to  deposit  their  eggs  in  the  now  nearly  fully  developed  straws. 
The  eggs  are  placed  just  above  the  uppermost  joint  accessible  to  the 
female,  usually  the  second  or  third  below  the  head.  But  a  single  egg 
is  deposited  in  a  place,  the  object  of  the  mother  insect  seeming  to  be 
to  get  it  in  the  center  of  the  stem  in  the  more  or  less  solid  portion 


a 

6. — Method  of  oviposition  of  female 
summer  form  (Isosoma  grande, 
Riley):  a,  female  inserting  her  eggs; 
b,  section  of  wheat  stem  showing  point 
reached  by  oviposition  (after  Riley). 


Fig. 
of 


21 

just  above  the  joint.  The  eggs,  as  with  those  of  the  spring  brood,  hatch 
in  a  short  time,  and  the  larvae  reach  maturity  by  the  time  the  straw 
has  become  too  tough  and  dry  to  afford  further  nutriment.  The  larva 
at  this  time  usually  gnaws  its  way  down  into,  or  at  least  partly  into, 
the  joint,  and  without  forming  cell  or  cocoon,  about  October  passes 
into  the  pupal  stage. 

DESCRIPTION. 

ADULTS   OF   SUMMER   FORM. 

(Isosoma  gr ancle  Riley.) 

Length  of  body,  4.2  mm.;  expanse,  7.0  mm.  Antennae  rather  more  slender  and 
less  clavate  than  in  the  spring  form  and  but  half  the  length  of  the  thorax.  Thorax 
with  the  mesonotum  slightly  more  rugulose;  wings  larger  and  less  hyaline  than  in 
the  winged  specimens  of  the  spring  form,  with  the  veins  extending  to  the  outer 
third,  the  submarginal  nearly  four  times  as  long  as  the  marginal;  legs  with  the 
femora  less  swollen.  Abdomen  not  so  long  as  the  thorax,  stouter  than  in  the  spring 
form,  ovate-acuminate,  approaching  typical  Eurytoma.  Less  hairy  than  in  the  spring 
form,  especially  about  the  legs,  the  hairs  about  the  abdomen  being  less  numerous, 
less  regular,  and  shorter.  Coloration  similar  to  that  of  the  spring  form,  but  brighter 
and  more  highly  contrasting,  the  promotal  spot  larger  and  brighter  yellow,  the 
pedicel  of  the  antennae  yellow,  and  the  femora  with  a  definitely  limited  suboval 
yellowish  spot  below,  near  the  tip,  extending  two-fifths  the  length  of  the  femur  on 
front  pair,  smaller  on  middle  pair,  and  still  shorter  and  less  definite  on  posterior 
pair. 

Larva  greenish  yellow  in  color.  Average  length,  6  mm. ;  otherwise  of  same  pro- 
portions and  structure  as  in  spring  form." 

Pupa,  average  length,  5  mm.  Except  in  larger  size  and  ample  wingpads  undis- 
tinguishable  from  that  of  the  spring  form,  minutum. 

Egg  of  the  ordinary  ovoid  form  with  pedicel  about  twice  as  long  as  the  bulbous 
part.  The  apical  end  is  furnished  with  a  distinct  hook,  perhaps  for  the  purpose  of 
holding  the  egg  in  place  while  the  ovipositor  is  being  withdrawn  from  the  plant. 

ADULTS    OF    SPRING    FORM. 

(Isosoma  minutum. ) 

Length  of  body,  2.8  mm. ;  expanse  of  wings,  4  mm. ;  greatest  width  of  front  wing, 
0.7  mm.;  antenna3,  subclavate,  three-fourths  the  length  of  thorax;  whole  body 
(with  exception  of  metanotum,  which  is  finely  punctulate)  highly  polished  and 
sparsely  covered  with  long  hairs  toward  the  end  of  abdomen;  abdomen  longer  than 
thorax  and  stouter.  Color,  pitchy  black;  scape  of  antennae,  occasionally  a  small 
patch  on  the  cheek,  mesoscutum,  femoro-tibial  articulations,  coxae  above  and  tarsi 
(except  last  joint)  tawny;  pronotal  spot  large,  oval,  and  pale  yellowish  in  color; 
wing  veins  dusky  yellow  and  extending  to  beyond  middle  of  wing;  submarginal 
three  times  as  long  as  marginal;  postmarginal  very  slightly  shorter  than  marginal, 
and  stigmal  also  shorter  than  marginal.     (See  Riley,  Am.  Nat.,  1882,  p.  247.) 

Larva,  length,  4.5  mm. ;  of  the  shape  indicated  in  fig.  3;  color  pale  yellow;  mouth 
parts  brownish.  Antenna-  appearing  as  short  two-jointed  tubercles.  Mandibles 
with  two  teeth.  Venter  furnished  with  a  double  longitudinal  row  of  stout  bristles, 
a  pair  to  each  joint.  Each  joint  bears  also,  laterally,  a  short  bristle.  Stigma  pale, 
circular;  ten  pairs,  one  on  each  of  joints  2  (mesothoracic)  to  11. 

Pupa,  jet  black  without  other  coloring;  smaller  than  that  of  summer  form.  That 
is  to  say,  the  pupae  wintering  over  in  the  straw  and  from  which  the  spring  form 
develops  is  thus  to  be  described;  that  following  the  larvae  developing  in  spring  is 
understood  to  belong  to  the  summer  form. 


« Riley,  Ann.  Rept.  CJ.  S.  Dept.  Agr.,  1884,  p.  58. 


22 


NATURAL   ENEMIES. 


Probably  the  most  efficient  enemy  of  this  species  is  a  small,  slender, 
four- winged  fly,  of  somewhat  brilliant  metallic-colored  body  and  yel- 
low legs.     This  has  a  very  slight  resemblance  to   an  Isosoma,  and, 
indeed,  was  described  as  Isosoma  allynii,  now  known  as   Eupelmus 
ally  nil  French.     A  somewhat  similar  insect  with  metallic  body  and 
yellow  abdomen,  Stictonotus  isosomatis  Riley,  is  very  efficient  in  destroy- 
ing the  larvae  in  the  straw.     Homojpor%is  (Semiotellus)  chalcidephagus 
Walsh  and  beyond  a  doubt  other  chalcids  are  also  instrumental  in  hold- 
ing it  in  check.      These  parasites  are  all  the  more 
efficient  as  they  are  double-brooded  also,  developing 
in  late  summer  and  at  once  ovipositing  in  other  larvae. 
There  is  also  an  egg  parasite  that  I  have  reared  in 
connection  with  Isosoma,  but  not  with  certainty  from 
this  species.     This  is  Oligosita  americana  Ashmead 
MS.     As  in  all  cases  where  I  have  obtained  this  there 
were  species  involved  other  than  the  one  under  con- 
sideration, it  is  obviously  impossible  to  say  that  it 
destroys  the  eggs  of  this  species,  but  with  such  regu- 
larity does  it  occur  in  connection  with  Isosoma  in 
fig.  i.^Pedicuioides    general  that  no  doubt  it  preys  upon  this  one  with  the 
ventHcoms  Newp., a    others.     When  the  wheat  is  harvested  the  straw  is 
the  larva— much    frequently,   and,   in  fact,  almost  invariably,  cut  off 
enlarged  (after  Mar-    between  joints,  thus  leaving  the  larvae,  if  there  are 
such  in  the  straws  at  that  point,  exposed  to  attack 
from  predaceous  insects.     The  larvae  of  a  small,  slender,  black  and 
yellow   carabid    beetle    (Leptotrachelus    dorsalis    Fab.)    crawls    up, 
descends  into  the  stubble  and  devours  the  Isosoma  larvae,  but  unfor- 
tunately its  taste  seems  to  be  too  obtuse  to  allow  it  to  confine  itself 
strictly  to  Isosoma,  and  as  a  consequence  it  devours  parasites  as  well 
as  host.     The  mite  Pedicidoides  {Heteropus)  ventricosus  (fig.  7)  is  also 
an  enemy,  gaining  access  to  the  larvae  precisely  as  with  the  beetle 
larvae  previously  mentioned. 

PREVENTIVE  AND  REMEDIAL  MEASURES. 

The  fact  of  the  spring  brood  being  almost  entirely  wingless  and 
therefore  unable  to  fly  from  field  to  field  places  it  almost  totally  at  the 
mercy  of  the  farmer,  as  he  has  but  to  change  his  crop  from  one  field 
to  another  to  rid  himself  of  its  presence.  It  is  true  the  summer  form 
can  fly  about  from  field  to  field  at  will,  and  it  does  so,  but  if  the  spring 
brood  of  adults  are  left  helpless  in  a  field  with  no  wheat  plants  in  which 
to  place  their  eggs,  it  will  be  seen  at  once  that  there  can  be  no  sum- 
mer brood  emanating  from  this  source.  Rotation  of  crop  will  as  a 
consequence  be  sufficient  to  prevent  an  overabundance  of  this  species. 
But  there  are  conditions  under  which  this  is  not  practicable,  as  in  some 


23 

sections  and  with  some  farms  tne  soil  is  but  little  fitted  for  other  crops, 
and  where  wheat  follows  wheat  year  after  year  for  an  indefinite  period. 
Under  such  conditions,  burning  the  stubble  before  preparing  the 
ground  for  the  new  crop  in  fall  will  prove  effective.  If  this  burning 
is  delayed  until  September,  many  of  the  parasites  will  have  developed 
and  escaped.  The  burning  can  be  best  carried  out  by  cutting  the  grain 
as  high  as  possible,  leaving  the  stubble  long.  A  few  days  before 
burning  a  mower  should  be  run  over  the  field,  cutting  off'  all  grass  and 
weeds,  which,  when  dried,  will  add  to  the  fuel  supplied  by  the  stubble. 
Taking  advantage  of  a  favorable  wind,  the  farmer  can  burn  over  his 
field  cleanly,  thereby  not  only  ridding  it  of  the  presence  of  this  pest, 
but  also  the  Hessian  fly,  besides  burning  up  much  of  the  seed  of  foul 
weeds  and  grasses. 

DISTRIBUTION. 

This  species  seems  to  occur  throughout  the  middle  belt  of  country 
from  the  Atlantic  to  the  Pacific,  wherever  wheat  is  grown  as  a  staple 
crop.  Whether  it  is  single- brooded  in  the  North  and  is.  therefore,  in 
such  countries  capable  of  sustaining  itself  in  spring  wheat,  is  not  yet 
known.  Having  no  other  known  food  plant  than  wheat,  it  will  neces- 
sarily follow  that  its  range  will  be  restricted  to  areas  of  wheat  culti- 
vation, and  being  double  brooded,  requires  fall  wheat  in  which  to 
develop.  The  fact  of  its  having  been  so  long  confused  with  what  now 
seems  the  true  joint-worm  fly  (Isosoma  tritici  Fitch)  renders  its  actual 
distribution,  as  well  as  the  extent  of  its  ravages  in  the  past,  somewhat 
obscure.  I  found  the  summer  form  (grande)  in  considerable  numbers 
in  spring  wheat  at  Lafayette.  Ind.,  June  19,  18i>5,  and  it  is  likely  that 
it  can  breed  therein,  though  fall  wheat  is  necessary  for  form  minutum. 

THE  JOINT-WORM. 
(Isos&ma  tritici  Fitch.     Fijjrs.  S  and  9.) 

I  have  previously  referred  to  the  confusion  of  Isosoma  tritici  Fitch 
with  I.  hordei  Harris,  and  which  was  so  persistently  insisted  upon  by 
Walsh  and  Riley.  It  was  not  until  1896  that  Dr.  Howard  succeeded  in 
establishing  the  fact  that  this  is  a  valid  species,  and  now  we  are  con- 
fronted with  a  long  series  of  complications  that  can  only  be  safely 
corrected  by  carefully  rearing  both  species  and  studying  them  anew. 
Failing  entirely  in  securing  sufficient  material  from  wheat  in  carrying 
out  the  investigations  upon  which  this  bulletin  is  based,  I  feel  now 
very  much  like  letting  the  insect  alone  until  an  opportunity  is  offered 
to  untangle  the  knotted  skein.  Doctor  Fitch  stated  distinctly  that  the 
term  "joint-worm"  was  to  be  applied  to  the  insect  attacking  wheat, 
and  it  was  because  of  the  mistake  of  considering  it  the  same  insect  as 
that  described  by  Harris  that  the  name  "joint-worm"  came  to  be 
applied  to  I.  hordei  at  all;  a  mistake  that  belongs  neither  to  Harris 
nor  Fitch,  but  one  that  has  misled  nearly  everybody. 


24 


PREVIOUS    RECORD    OF    THE    INSECT. 


About  the  year  1848,  in  central  Virginia,  throughout  the  country 
adjacent  to  Charlottesville,  Albemarle  County,  and  Gordonsville, 
Orange  County,  the  wheat  began  to  suffer  seriously  from  attack  of 
what  was  at  that  time  called  the  joint-worm.  In  1851  the  wheat  in 
Albemarle  County  was,  much  of  it,  not  worth  the  harvesting.  In 
1854  the  ravages  of  the  pest  had  become  so  serious  that  a  "  joint- worm 
convention  "  was  held  in  Warren  ton  to  devise  means  for  controlling  it 
and  preventing,  if  possible,  its  further  ravages,  as  by  this  time  it  had 
become  almost  impossible  to  raise  wheat  at  all  in  the  infested  terri- 
tory. The  action  of  this  convention  was  to  recommend  a  better  sys- 
tem of  cultivation,  the  use  of  guano  and  other  fertilizers  to  promote 
the  rapid  growth  and  early  ripening  of  the  grain,  and  the  burning  of 
the  stubble  after  harvest. 


Fig.  8. — Isosoma  tritici  Fitch:  adult  of  the  joint-worm,  much  enlarged  (from  Howard). 

Looking  back  to  this  period,  our  later-day  entomologists  can  hardly 
understand  how  there  should  have  been  any  difficulty  in  determining 
beyond  a  possible  doubt  the  author  of  all  of  this  destruction.  Doctor 
Fitch,  who,  it  seems,  received  some  of  the  growing  wheat  plants 
infested  with  the  larvae  from  that  locality,  always  insisted  that  he  found 
a  cecidomyian  larvae  inhabiting  cells  like  those  occupied  by  the  joint- 
worm  and  that  these  were  the  true  depredator,  and,  though  he  continued 
to  stoutly  defend  his  determination,  we  have  yet  to  discover  a  Cecido- 
myia  either  causing  or  inhabiting  such  a  cell  or  gall  in  the  wheat  plant. 
From  all  that  has  been  since  learned  relative  to  these  insects  it  is  clear 
that  the  ravages  were  those  of  this  species,  with,  perhaps,  individuals 
of  the  preceding  species  intermixed  among  them.  As  a  matter  of 
history  it  may  be  stated  that  Doctor  Fitch  was  still  unconvinced  that 
the  joint-worm,  and  not  a  dipterous  insect,  was  responsible  for  the  dam- 


ite  as  1859  he  expressed  astonishment  that  he  was 

any  Hessian  flies  from 


age  in  Vi 
unable  to  rear 
the  same  straw  from  which  he  reared 
the  joint-worm.  Surely  the  unento- 
mological  farmer  might  be  pardoned 
for  falling-  into  the  same  error  until, 
at  least,  he  is  placed  in  possession  of 
some  way  of  distinguishing*  them  from 
each  other. 

After  finding  out  beyond  question 
that  this  is  a  valid  species,  that  it  is  the 
true  joint-worm  fly  attacking  wheat 
and  not  barley,  while  Is<>s<>m<i  hordei 
attacks  barley  and  not  wheat,  notwith- 
standing the  effect  on  the  straw  is  much 
the  same,  and  that  though  it  resembles 
IsosoitKt  grande  rather  closely,  it  is 
quite  different  in  habits  and  life  his- 
tory, we  are  forced  to  conclude  that 
we  really  know  very  little  about  it.  I 
have  reared  it  in  limited  numbers  from 
wheat  straw  in  Illinois,  Indiana,  and 
Ohio,  though  it  would  appear  that 
about  1885  it  became  excessively  abun- 
dant in  some  parts  of  Michigan,  and, 
in  fact,  I  am  not  sure  but  that  I  have 
myself  found  the  larva1  in  some  abun- 
dance, but  supposed  them  to  belong  to 
the  preceding  species.  The  uncer- 
tainty in  regard  to  the  identity  of  these 
larvae  was  owing  to  the  fact  that  at  the 
time  they  were  observed  this  was  not 
considered  a  valid  species,  and  I  at  that 
time  considered  them  as  belonging  to 
Isosoma  grande,  but  now  doubt  my 
former  opinion  from  the  fact  that  this 
species  does  not  always  form  galls 
either  in  wheat  or  Elymus,  that  there 
were  several  larva'  between  the  joints 
instead  of  one.  and  that  they  were 
located  just  under  the  inner  walls  of 
the  straw,  but  not  forming  a  cell, 
whereas  those  of  the  species  last  con- 
sidered is  found  only  in  the  center  of 
the  straw,  in  the  more  solid  sub- 
stance, immediately  above  the  joint 
SfiSO— No.  42—05 4 


Fig.  9.— Effect  of  joint-worm  in  wheat  straw 
(drawn  in  Division  of  Entomology) . 


26 

itseJf.  In  1885  Professor  Cook  described  Isosoma  nigrum,  which  he 
states  was  reared  from  larvae  forming-  creases  and  hardened  deformities 
in  the  straw.  Professor  Cook's  specimens,  sent  to  Washington,  have 
been  determined  by  Doctor  Howard  as  Isosoma  trltici  Fitch. °  (See 
also  Walsh,  Trans.  111.  St.  Agl.  Soc,  vol.  5,  pp.  185-490,  figs.) 

LIFE    HISTORY. 

The  larvae  pass  the  winter  in  the  straw,  if  in  wheat,  and  in  the  stems 
of  Virginia  rjre  grass  ( Elymus  virginicus)  in  the  East,  and  E.  glaucus 
and  another  grass,  either  JBromus  ciliatus  or  a  species  of  Agropyron, 
in  California. 

In  the  Middle  West  the  adults  appear  the  latter  part  of  May  and 
early  June.  The  egg  does  not  differ  materially  from  that  of  I.  grande, 
and  it  is  probable  that  the  method  of  oviposition  is  much  the  same  as 
in  that  species,  the  female  placing  her  eggs  in  the  young  growing 
wheat  plant  just  above  the  uppermost  joint  to  which  she  can  secure 
access  at  the  time.  Ordinarily  the  upper  joint  is  not  yet  uncovered, 
except  in  case  of  very  early  wheat,  and  in  that  which  has  made  less 
advance  even  the  second  joint  from  the  head  is  so  covered  with  the 
sheaths  that  the  insect  is  unable  to  determine  its  position,  so  that 
sometimes  we  find  more  larvae  between  the  second  and  third  joints 
than  we  do  farther  up  between  the  first  and  second,  precisely  as  with 
L  grande.  The  larvae  reach  their  full  growth  by  harvest,  but  do  not 
pupate  until  the  following  spring. 

All  adults  are  winged,  and  both  sexes  are  represented.  Outside  the 
wheat  field  I  have  reared  the  insect  only  from  Elymus  virginicus,  and 
I  question  its  breeding  in  the  stems  of  cheat  {Bromus  secalinus)  for 
the  reason  that  I  have  reared  it  from  the  rye  grass  and  not  from  the 
cheat,  though  both  were  abundant  in  the  same  locality.  Mr.  Koebele, 
who  reared  it  from  Elymus  glaucus  in  California,  was  uncertain 
whether  he  also  reared  it  from  Bromus  ciliatus  or  Agropyron.  Both 
the  Bromus  mentioned  by  Koebele  and  Agropyron  repens  occur  in  the 
East,  and  it  is  very  probable  that  future  studies  of  the  species  will 
show  that  there  are  other  grasses  besides  rye  grass  that  will  require 
attention  from  the  farmer  who  wishes  to  guard  against  its  appearance 
in  his  fields  by  preventing  its  breeding  permanently  along  roadsides 
and  the  borders  of  his  fields. 

DISTRIBUTION. 

Doctor  Fitch  received  this  insect  from  Maryland,  Doctor  Lintner  and 
Professor  Comstock  reared  it  in  New  York,  the  United  States  Depart- 
ment of  Agriculture  has  it  from  Virginia  and  North  Carolina,  Pro- 
fessor Cook  reared  it  in  Michigan,  I  have  reared  it  in  Ohio  and  Illinois 

"Grass  and  Joint-worm  Flies  and  their  Allies,  Tech.  Ser.  2,  Div.  Ent.,  U.  S. 
Dept.  Agr.,  p.  18. 


27 

and  found  it  in  Indiana,  Doctor  Fletcher  lias  reared  it  in  Ontario, 
Canada,  and  Mr.  Koebele  in  California,  and  there  is  hardly  a  doubt  that 
investigations  will  reveal  its  presence  throughout  the  entire  wheat- 
growing  region  of  North  America.  Being  fully  winged  and  single 
brooded,  as  well  as  capable  of  breeding  in  abundance  outside  of  the 
grain  fields,  there  seems  no  good  reason  why  it  should  not  cover  the 
whole  country,  attacking  either  spring  or  winter  wheat. 

DESCRIPTION. 

"Female. — Length  4  mm.;  expanse  7.t>  mm.  Head,  pronotum,  and  mesonotum 
strongly  rugulose  but  not  umhilicate-puuctate  except  toward  tip  of  scutellum,  where 
an  occasional  umbilicate  puncture  occurs;  metanotum  also  strongly  rugulose,  with  a 
faint  trace  anteriorly  of  a  median  longitudinal  furrow;  metanotal  spiracles  large  and 
perfectly  circular;  pronotal  spots  moderately  large  and  often  faint,  but  plainly  dis- 
cernible from  above,  sometimes,  however,  quite  bright  and  distinct,  Abdomen 
longer  than  thorax,  nearly  as  long  as  head  and  thorax  together;  abdominal  segments 
4  and  5  together  longer  than  2,  3  only  about  half  as  long  as  4,  and  5  as  long  as  two 
preceding  united;  first  funicle  joint  one-half  longer  than  second;  club  longer  than 
three  preceding  funicle  joints  together.  Body  slightly  but  plainly  julose  except  at 
sides  of  metanotum,  where  the  fimbria  is  very  obvious.  Legs  black  except  at  joints, 
which,  with  the  tarsi,  are  yellow.     Claw  of  stigmal  club  given  off  before  the  tip. 

Male. — Length,  2.9  mm.;  expanse,  6  mm.  Petiole  shorter  than  hind  coxa3,  faintly 
punctate;  flagellum  of  antemne  uniformly  pilose,  joints  well  rounded  above,  not 
strongly  pedicellate;  joint  1  three  times  as  long  as  wide  and  nearly  three  times  as 
long  as  pedicel;  none  of  the  funicle  joints  constricted  in  the  middle;  joints  2  and  3  each 
nearly  as  long  as  1 ;  joints  4  and  5  each  a  little  shorter;  club  plainly  divided  by  a 
distinct  incision  into  two  joints,  but  the  terminal  ovate  joint  is  not  pedicellate." 
Howard,  Tech.  Ser.  2,  Div.  Ent.,  U.  S.  Dep.  Agr.,  pp.  17,  18. 

Originally  described  by  Fitch.  Jour.  N.  Y.  State  Agr.  Soc,  1859, 
p.  115.  Cited  as  Isosoma  hordei  by  Walsh,  Anier.  Ent.  and  Bot.,  II, 
p.  332.  Described  as  Decatoma  hasilaris  by  Provancher,  Faun.  Ent. 
Can.,  II,  p.  569. 

NATURAL   ENEMIES. 

The  natural  enemies  are,  with  few  exceptions,  probably  the  same  as 
with  the  preceding  species,  to  which  this  is  more  closely  related  than  with 
the  one  that  follows,  at  least  so  far  as  its  life  history  is  concerned.  In 
my  own  rearings  I  have  invariably  bred  this  in  connection  with  I. 
grande  if  from  wheat  straw,  or  with  /.  dymi  if  from  grass,  so  that 
personally.  I  am  not  able  to  say  that  certain  parasites  actually  came 
from  /.  tritici,  though  there  is  no  reason  for  doubting  that  such  was 
the  case.  Certain  parasites  do  most  certainly  confine  themselves  to 
particular  species  of  Isosoma.  Websterelhis  tritici  Ashm.  has  only 
been  reared  from  this  species,  as  it  is  now  known.  An  undescribed 
Isosoma  occurs  in  considerable  abundance  in  the  stems  of  Tricuspid 
St  sli  rioides,  and  from  this  I  have  reared  a  parasite  belonging  to  the 
genus  Toryrnus,  but   strangely  enough   this  parasite  has  only  been 


28 

reared  from  this  particular  Isosoma,  even  where  the  grass  infested  by 
its  particular  host  was  growing  in  the  midst  of  Elymus,  literally  alive 
with  the  larvae  of  three  other  species  of  Isosoma.  Thus,  while  some 
parasites  attack  all  of  the  species,  there  are  evidently  others  that 
restrict  themselves  to  one. 

'      REMEDIAL   AND    PREVENTIVE    MEASURES. 

Owing  to  its  possessing  wings  whereby  it  is  capable  of  flying  readily 
from  one  field  to  another,  or  breeding  in  the  stems  of  grasses  in  the 
intervening  territory,  a  rotation  of  crop  will  be  less  effective  in  the 
case  of  this  species  than  with  the  preceding.  For  the  same  reason, 
careful  attention  to  roadsides,  borders  of  fields,  and  ditches  becomes  all 
the  more  imperative.  The  burning  over  of  the  stubble  fields  before 
preparing  the  ground  for  wheat  again  in  the  fall,  or  the  same  treatment 
of  the  uncultivated  areas  above  mentioned  at  any  time  during  winter 
or  early  spring  will  effectually  exterminate  these  insects  where  these 
measures  are  carried  out.  In  the  Middle  West  wheat  seldom  follows 
wheat  on  the  same  ground  for  a  series  of  years,  the  grain  being  rotated 
with  red  clover,  which  prevents  the  burning  over  of  the  stubble  fields 
in  the  fall,  but  does  not  in  any  way  affect  the  treatment  of  grass  lands, 
and  if  the  crop  is  rotated  annually  and  the  borders  and  waste  places 
attended  to  there  is  little  likelihood  of  the  farmer  suffering  greatty 
from  the  depredations  of  this  insect.  I  have  invariably  found  the 
most  serious  injuries  to  occur  on  thin  or  poorly  fertilized  soils  or 
where  the  land  had  not  been  thoroughly  prepared  before  seeding. 
Probably  whatever  tends  to  produce  a  healthy,  vigorous  growth  of 
the  wheat  plant  will  tend  to  discourage  oviposition  b}^  the  insect.  It 
is  not  known  that  the  insect  prefers  one  variety  of  wheat  to  another, 
but  the  variety  with  the  stoutest  straw  will  probably  suffer  least  from 
attack. 

DIFFICULTY   IN   RECOGNIZING    THE    SPECIES. 

I  have  made  no  attempt  to  describe  the  larva  and  pupa  in  their  proper 
place,  because  I  do  not  believe  they  can  be  separated  by  any  descrip- 
tion from  those  of  the  preceding  species  if  in  wheat,  or  those  of  Isosoma 
elymi  French  if  in  grass.  Notwithstanding  this  the  farmer  can  readily 
separate  them,  at  the  proper  season  of  the  year,  even,if  both  ara-presjent 
in  his  cultivated  fields.  After  October  this  species  will  be  in  the  form 
of  a  yellowish  white  larva  in  the  stubble,  while  the  preceding  species 
will  be  in  the  form  of  a  black  pupa,  both  perhaps  in  the  center  of  the 
stubble.  In  spring  the  larvse  of  this  species  will  change  to  a  jet  black 
pupa,  while  those  of  I.  grande  will  have  developed  and  escaped.  So, 
then,  pupae  found  in  the  fall  will  probably  belong  to  the  preceding 
species;  those  found  in  spring,  if  in  wheat,  to  this,  and  larvse  found 
after  October,   if  in  wheat  stubble,  also  to  this  species.     However, 


29 

too  much  reliance  must  not  be  placed  on  these  distinctions,  as  there  are 
other  supposed  species  of  these  insects  attacking  wheat  of  whose  larva1 
and  pupa1  we  know  nothing,  but  with  our  present  knowledge  the  facts 
just  given  are  the  best  that  can  now  be  offered  the  farmer  in  order  to 
enable  him  to  separate  the  different  main  enemies  of  his  grain  and 
receive  whatever  practical  benefit  is  possible  from  what  information  is 
now  available,  leaving  future  studies  to  throw  more  light  upon  his 
problems.  The  adults  can  be  easily  separated  from  those  of  the  pre- 
ceding species  by  their  smaller  size,  and  from  the  next  by  their  smaller 
size  and  the  color  of  the  legs,  which  in  /.  hordei  are  honey  yellow. 
The  larvae  are  also  smaller  than  those  of  the  following  species  and  ma}' 
or  may  not  cause  galls  and  deformities  in  the  straw.  The  adults  of  the 
summer  form  of  the  preceding  and  those  of  the  following  species  are 
abroad  at  the  same  time  as  are  those  of  this  species  during  the  last 
days  of  May  and  early  June. 

While  fig.  9  illustrates  the  effect  of  the  larvae  on  a  wheat  plant,  there 
are  so  many  variations  from  this  that  it  is  at  present  impossible  to 
separate  these  two  gall-forming  species  by  their  effect  on  the  straw. 

THE  BAILEY  STRAW-WORM. 

(Isosoma  hordei  Harris.     Fig.  10.) 

Up  to  1896  this  species  was  confused  with  the  preceding  and  the 
term  " joint- worm"  applied  thereto.  The  fact  is,  Harris  seems  not  to 
have  given  this  name  to  his  species  at  all,  but  on  the  other  hand  Doc- 
tor Fitch  applied  it  to  his  I.  tritici,  and  it  was  owing  to  the  confusion 
of  these  two  insects  that  the  name  became  misapplied,  and  1  have  here 
given  Harris's  species  the  name  "barley  straw- worm,"  in  accordance 
with  the  name  hordei. 

PREVIOUS    RECORDS    OF    THE    INSECT. 

Of  all  of  our  described  species  of  Isosoma  this  was  the  earliest 
known  and  was  for  many  years  supposed  to  be  the  only  species  infest- 
ing cultivated  grains  or,  in  fact,  inhabiting  this  country,  as  it  was  con- 
sidered a  parasite  on  the  real  depredator,  presumed  to  be  some  kind 
of  a  two-winged  fly,  and  was  actually  described  by  Dr.  W.  T.  Harris 
in  1830  as  a  parasite,  under  the  name  Ichneumon  hordei/1  Doctor 
Harris  certainly  seems  to  have  been  aware  of  the  fact  that  as  early 
as  1821  Mr.  James  Worth,  of  Sharon,  Bucks  County,  Pa.,  found 
larvae  clearly  belonging  to  some  species  of  Isosoma  affecting  the  culms 
of  wheat  i;near  the  root,  where  they  caused  enlargements  of  the 
stem;"6  and  in  1823,  Mr.  Joseph  E.  Muse,  of  Cambridge  (Eastern 
Shore),  Md.,  reared  an  insect,  also  from  wheat,  which  he  termed  a 

a  New  England  Farmer,  July  28,  1830;  Ins.  Mass.,  1841,  pp.  434-487. 
b  American  Farmer,  vol.  4,  p.  394. 


30 


\ 


^<^ 


"Tenthredo,"  whose  larvae,  as  he  stated,  "  burrow  within  the  stems 
and  feed  upon  them."a  Doctor  Harris,  in  the  edition  of  1841  of  his 
Insects  of  Massachusetts,  page  431,  refers  to  the  statement  of  Dr. 
Andrew  Nichols,  of  Danvers,  who  stated  that  worms  found  in  his 
barley  straw  were  about  one-tenth  of  an  inch  in  length  and  of  a  yel- 
low or  straw  color,  and  that  in  the  month  of  November  they  appeared 
to  have  passed  into  the  chrysalis  state,  but  living  through  winter 
unchanged  in  the  straw.  The  insects  referred  to  by  Mr.  Worth,  of 
Pennsylvania,  and  Mr.  Muse,  of  Maryland,  might  quite  probably  have 
been  Isosoma  tritici  Fitch,  but  if  the  one  referred  to  by  Doctor  Nichols 
was  an  Isosoma  at  all  it  was  certainly  I.  grande,  as  that  is  the  only 
species  attacking  grain  that  is  known  to  pupate  in  the  fall.  Thus  it 
will  be  seen  that  it  is  not  easy  to  determine  just  what  Harris  might  have 
included  as  belonging  to  his  I.  hordei,  though  he  nowhere  states  that  it 

was  ever  obtained  from 
any  other  than  barley 
straw;  hence  the  name, 
Jwrdei,  applied  to  it.  It 
is  interesting  to  know 
that  specimens  labeled  in 
his  handwriting  "Para- 
sitic in  barley,  June  15, 
1830,"  are  still  in  the 
museum  of  the  Boston 
Society  of  Natural  His- 
tory, so  that  there  can 
be  no  mistake  in  the 
identity  of  the  insect 
described.  Even  in  the 
edition  of  his  Insects  of 
Massachusetts,  of  1841,  Harris  makes  no  mention  of  his  species  having 
been  found  affecting  wheat.  In  the  edition  of  1852  he  relates  that 
about  eight  }^ears  before  children  sleeping  on  straw  beds  in  Cam- 
bridge, Mass. ,  had  been  bitten  by  these  insects  and  the  annoyance"  had 
been  so  great  that  the  beds,  both  straw  and  ticks,  had  been  burned. 
Now  people  do  not  use  barley  straw  for  such  domestic  purposes,  nor 
in  fact  do  they  use  wheat  straw  as  a  rule,  but  oat  straw.  As  Doctor 
Harris  does  not  enlighten  us  as  to  what  kind  of  straw  it  was  from 
which  the  insects  annoying  the  children  came,  we  still  have  no  direct 
proof  that  this  species  was  ever  known  in  connection  with  wheat  straw. 
About  1852  there  appeared  a  similar  trouble  in  the  barley  in  cen- 
tral New  York,  and  though  Doctor  Fitch  described  it  as  a  distinct 
species  under  the  name  Eurytoma  fulvipesf  we  now  know  that  it  was 

«Loc.  cit.,  vol.  5,  p.  113. 

6  Jour.  N.  Y.  Agricultural  Soc,  Vol.  IX,  p.  115. 


Fig.  10. — Isosoma  hordei  Harris:  adult  of  the  barley  straw-worm 
(from  Howard). 


81 

Isosoma  hordel.  This  last  outbreak  in  central  New  York  appears  to 
have  been  rather  widespread  and  disastrous,  for  in  1858  Hon.  George 
Geddes,  president  of  the  State  Agricultural  Society,  stated  that  while 
formerly  a  yield  of  -io  bushels  of  barley  to  the  acre  was  expected,  they 
could  not  at  that  time  rely  upon  more  than  20,  and  unless  relief  came 
barley  growing,  on  account  of  the  attack  of  this  pest,  would  have  to 
be  abandoned.'' 

There  was  a  local  outbreak  of  this  species  in  Ontario,  Canada,  in 
1867-68,  and  observed  at  Wakeman,  Chagrin  Falls,  and  Barry,  Ohio; 
Indiantown,  Cuckoo,  and  Paynes,  Va. ;  Albany,  X.  Y. ;  Canada  West 
(William  Couper);  Ottawa,  Canada;  and  Urbana,  Carbondale,  and 
Marshall,  111.  So  far  it  has  not  been  reported  from  the  Pacific  coast 
States.  Doctor  Fitch  confined  this  species  to  the  insect  reared  by 
Harris  in  Massachusetts,  and  the  one  working  the  injuries  in  central 
New  York  as  Isosoma  fulvipes,  both  of  which  are  now  known  to 
belong  to  h<>x<>nt<i  hordei. 

LIFE    HISTORY 

The  species  is  single  brooded.  The  adults  of  both  sexes,  all  fully 
winged,  emerge  from  the  straw  and  grass  in  late  May  and  earh^  June, 
ovipositing  almost  immediately.  The  effect  of  the  larva3  on  the  grow- 
ing plants  begins  to  show  within  a  short  time,  and.  though  the  larvae 
become  full  grown  during  June  and  early  July,  they  remain  in  this 
condition  within  their  cells  until  May  of  the  following  year. 

EFFECT    OF    THE    LARViE    ON    THE    PLANT. 

The  eggs  may  be  deposited  in  the  stem  of  barley  or  grass  anywhere 
between  the  root  and  the  head,  even  among  the4  lower  spikelets  of  the 
head.  The  effect  of  the  larvae  may  be  to  cause  hard,  woody  cells, 
whose  outline  is  indicated  only  by  slight  discolorations,  the  outer  sur- 
face of  the  stem  being  smooth  and  not  in  the  least  swollen,  the  cell 
being  entirely  within  the  walls  of  the  stem,  causing  no  distortion  in 
the  straw;  or  there  may  be  anywhere  from  one  to  a  dozen  galls  in  a 
cluster,  and  these  may  be  either  clearly  defined  or  so  packed  together 
and  cramped  as  to  lose  all  semblance  to  the  typical  galls  and  take  on 
the  appearance  of  diminutive  growths,  resembling  the  black  knot  of 
the  cherry  and  plum.  The  straw  or  grass  stem  may  be  enlarged  to 
two  or  three  times  its  natural  size,  forming  an  elongated  oval  woody 
growth  that  pushes  its  way  outward,  bursting,  as  it  were,  the  sheath 
at  base,  and  showing  between  the  edges.  This  growth  is  usually  on 
one  side  of  the  stem,  just  above  the  joint,  and  is  marked  with  inter- 
lacing creases  and  furrows  indicating  the  outlines  of  each  individual 
cell,  and  in  many  cases  sending  downward  from  the  lower  extremity 
small  root-like  appendages,  the   use  or  cause  of  which  it  is  difficult 

«  Tran*.  X.  Y.  Agl.  Soc,  1859,  p.  332. 


32 

to  understand.  All  of  these  malformations  as  well  as  others  may 
be  found  in  the  stems  of  Ely/nus  canadensis  in  abundance,  from 
which  swarms  of  the  adults  will  emerge  in  late  May  and  earty  June. 
Owing  to  the  woody  nature  of  these  abnormal  growths,  straw  attacked 
by  this  species  is  more  likely  to  be  broken  up  into  small  bits,  and 
these  go  in  with  the  grain  at  thrashing,  thereby  increasing  the  dan- 
ger of  transportation  from  one  localhVy  to  another,  but  to  offset  that, 
as  it  were,  there  is  likely  to  be  a  greater  proportion  of  the  insects 
left  in  the  stubble  than  with  the  other  species,  as  the  affected  straws 
are  usually  more  stunted  in  growth  and  shorter.  At  present  there  is 
no  other  insect  attacking  wheat,  rye,  or  barley  that  causes  similar 
growths  in  the  straw  except  Isosoma  tritici  Fitch,  in  wheat,  and  the 
farmer  can  hardly  mistake  the  work  of  these  two  pests  for  those  of 
any  other  in  his  fields. 

DESCRIPTION. 

" Female. — Length,  3.6  mm. ;  expanse,  6  mm.  Pronotum  and  mesonotum  minutely 
but  strongly  rugulose,  smoother  than  I.  tritici;  metanotum  more  coarsely  rugulose, 
the  larger  elevations  taking  a  longitudinal  direction,  no  central  furrow  or  carina; 
pronotal  spot  very  small,  not  visible  from  above.  Abdomen  as  long  as  head  and 
thorax  together;  joints  4,  6,  and  7  subequal  in  length,  the  fifth  a  little  longer;  joint 
3  a  little  longer  than  4,  2  hardly  longer  than  3  and  4  united;  funicle  joints  2  to  5  sub- 
moniliform,  but  still  a  little  longer  than  broad.  All  legs  (except  coxse)  and  antennae 
honey-yellow,  flagellum  and  femora  a  little  darker;  claw  of  stigmal  club  straight, 
given  off  well  before  tip  of  club;  pilosity  sparse. 

"Male. — The  only  males  which  I  have  seen  are  the  two  from  the  Harris  collection 
These  are  both  in  very  bad  condition;  neither  had  an  abdomen  and  one  has  no 
antennae.  With  the  other,  but  three  funicle  joints  remain  on  the  left  antenna  (the 
others  being  broken  off)  and  four  on  the  right,  but  the  latter  are  still  inclosed  in  the 
pupal  sheath.  The  three  funicle  joints  remaining  on  the  left  antenna  are  not  pedi- 
cellate, very  slightly  arched  above,  and  furnished  with  close,  moderately  short  hair 
not  arranged  in  whorls;  joint  1  longest,  2  and  3  successively  decreasing.  Joint  4  is 
still  shorter,  judging  from  the  sheathed  right  antenna."  (Howard,  Tech.  Ser.  2, 
Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  18,  19.) 

The  foregoing  description  was  drawn  up  from  specimens  in  the 
Fitch  collection,  labeled,  in  Fitch's  handwriting,  "  Enrytoma  fulvipes 
Fh. ;"  other  specimens  from  the  Harris  collection,  reared  from  barley, 
June  15,  1830;  other  specimens  from  "Canada  West," and  still  others 
reared  by  myself  from  stems  of  Elymus  canadensis  growing  near 
Champaign,  111.  This  is  the  Ichneumon  hordei  described  by  Harris 
in  the  New  England .  Farmer,  the  Eurytoma  fulvipes  described  by 
Fitch  in  his  seventh  report,  and  the  Isosoma  hordei  mentioned  by 
Walsh  in  the  American  Entomologist  (Vol.  II,  p.  330). 

The  larva,  except  from  its  larger  size  and  habit  of  living  within  a 
cell,  is  not  distinguishable  from  that  of  the  other  species  of  grain- 
infesting  Isosoma.  It  is  little  larger  than  that  of  I  grande,  found  in 
May  and  early  June,  and  it  has  the  universal  yellowish-white  color. 
The  same  may  be  said  of  the  pupa. 


33 


NATURAL    ENEMIES. 


The  larvae  appear  to  suffer  more  from  the  inroads  of  natural  enemies 
than  do  those  of  other  species  of  these  insects,  perhaps  because  of 
their  inhabiting'  the  walls  instead  of  the  center  of  the  straws,  thereby 
rendering-  them  more  accessible.  It  may  be  that  this  is  the  older  form, 
and  a  greater  number  of  the  parasitic  species  have  become  adapted  to 
it  as  a  host  insect.  There  is  little  doubt  that  Oligosita  americana 
Ashm.  and  Polyneura  citripes  Ashm.  both  attack  and  destroy  the 
eggs,  as  I  have  reared  them  in  numbers  from  stems  of  Elymus  inhab- 
ited by  the  larvae,  and  also  the  stems  of  other  grasses  inhabited  by 
other  Isosoma  lame.  Eujpehnus  allynii  French,  easily  known  by  its 
slender  body,  metallic  color,  with  yellow  legs,  is  associated  with  this 
as  it  is  with  nearly  all  other  species  of  these  insects  that  inhabit  the 
stems  of  grain  and  grass.  Merisus  isosomatis  Riley,  conspicuous  for 
its  yellow  body,  is  almost  as  abundant  as  the  preceding,  and,  as  the 
name  implies,  is  parasitic  on  other  species  also.  Homojporus  chalci- 
dephagus  Walsh  is  also  a  parasite,  but  I  have  reared  it  in  lesser  num- 
bers than  the  other  two,  in  Illinois.  Indiana,  and  Ohio.  Almost  the 
first  parasitic  species  that  I  reared  in  connection  with  the  present 
studies  of  Isosoma  hordei  was  a  second  new  genus  and  species.  Para- 
pteromaltbs  isosomatis  Ashmead  aIS.  I  have  myself  witnessed  the 
oviposition  of  all  of  these  parasitic  species,  and  their  life  history  is 
probably  practically  the  same.  The  adults  emerge  in  spring  a  little 
later  than  those  of  the  Isosoma,  but  there  is  a  second  generation  of 
adults  in  summer,  and  it  is  these  that  I  have  observed  placing  their 
eggs  in  the  cells  of  I.  hordei,  thus  doubling  their  effectiveness  in  hold- 
ing it  in  restraint  and  preventing  more  frequent  and  greater  devasta- 
tions in  the  grain  fields  of  the  farmer.  While  carrying  on  the  present 
investigation  I  have  reared  an  undetermined  Eurytoma,  a  parasite  on 
Isosoma,  but  as  I  reared  four  species  of  the  latter  from  the  same  lot 
of  stems,  it  is  impossible  to  say  to  what  extent  it  preys  upon  the  one 
now  under  consideration,  nor  do  I  know  anything  in  connection  with 
its  habits,  except  that  it  makes  its  appearance  in  spring,  simultaneously 
with  other  parasites. 

PREVENTIVE    M  EASURES. 

The  preventive  measures  might  well  be  summed  up  under  the 
caption  of  good  farming,  for  there  is  not  one  practical  measure  but 
will  pay  for  its  carrying  out.  aside  from  its  entomological  influ- 
ences. As  the  adults  are  fully  winged  and  can  fly  freely  from  one 
field  to  another,  less  must  be  expected  from  a  rotation  of  crop,  but 
even  under  these  conditions,  a  certain  amount  of  benefit  will  result 
from  a  careful  system  of  crop  rotation.  Wheat,  rye,  or  barley  should 
never  be  grown  on  the  same  land  for  more  than  two  years  in  succes- 
sion without  carefully  burning  over  the  stubble  before  preparing  the 


34       - 

ground  for  another  seeding.  To  these  must  be  added  the  mowing  off 
of  roadsides  and  along  fences  and  margins  of  fields  during  late  June 
or  early  July,  or  the  burning  over  of  these  during  winter  or  early 
spring,  thus  destroying  the  hibernating  larvae.  The  rye  grass  along 
the  margins  of  fields  and  ditches  should  receive  special  attention  in  the 
matter  of  mowing  and  burning.  It  is  not  known  whether  or  not  any- 
thing is  to  be  gained  by  early  sowing,  which,  besides,  is  apt  to  invite 
the  attack  of  Hessian  fly. 

THE  CAPTIVE  ISOSOMA. 

(Isosoma  captivum  Howard.     Fig.  11.) 

Very  little  is  known  of  the  habits  and  transformations  of  this  species. 
I  found  it  in  a  field  of  growing  rye  near  Normal,  111.,  May  10,  1884, 
and  swept  it  from  timothy  and  bluegrass  about  Lafayette,  Ind. ,  during 
May,  1885,  and  again  during  the  same  month  in  1886.  Dr.  J.  A. 
Lintner  reared  both  sexes  from  wheat  straw  sent  him  from  Johnsons 
Creek,  Niagara  County,  N.  Y.,  in  December,  1887,  the  adults  appear- 


Fig.  11. — Isosoma  captivum  How.:  achilt  (from  Howard). 

ing-  in  March  of  the  following  year,  the  straw  having,  presumably, 
been  kept  indoors  during  the  winter. a  Probably  the  adults  occur 
normally  at  about  the  same  time  as  those  of  Isosoma  hordei,  tritici, 
and  elymi.  We  know  that  it  attacks  wheat,  probably  rye,  and  perhaps 
barley. 

DESCRIPTION. 

"Female. — Length,  3.4  mm.;  expanse,  5.8  mm.  Head  and  mesonotum  uniformly, 
finely,  and  closely  rugulose,  not  shagreened;  metanotum  more  coarsely  rugulose  and 
with  a  narrow  and  shallow  central  longitudinal  groove,  which  widens  slightly  pos- 
teriorly;  pronotal  spot  plain,  moderately   large;    hind   coxae   delicately  punctate. 

« Fourth  Report,  State  Entomologist  of  New  York,  p.  34. 


35 

Abdomen  shiny,  as  long  as  thorax,  oblong-ovoid;  the  second  segment  occupying 
nearly  one-third  the  whole  surface;  segments  4  to  6  subequal,  the  third  a  little 
shorter;  funicle  joints  2  to  5  subequal;  club  nearly  as  long  as  three  preceding  joints; 
joint  1  one-half  longer  than  2;  pile  sparse  and  short,  more  marked  at  metanotal  iim- 
bria  and  terminal  joints  of  abdomen  than  elsewhere.  Color  uniform  black,  except 
for  pronotal  spot,  tarsi,  middle  and  hind  femoro-tibial  knees,  front  tibae  and  apical 
third  of  front  femora,  which  are  light  honey  yellow.  Stigma!  club  about  as  in  /. 
kageni  and  I.  agroslidis,  except  that  its  tip  is  more  rounded  instead  of  squarely  t  runcate. 
"Male. — Length,  2.5  nun.;  expanse,  5  mm.  Punctation  rather  finer  than  with 
female;  petiole  as  fong  as  first  abdominal  joint,  strongly  rugose;  flagellum  of  anten- 
nae long;  pedicel  not  globose,  slightly  elongate;  joint  1  of  funicle  longest,  twice  as 
long  as  pedicel;  joints  2,  3,  4,  and  5  each  a  little  shorter  than  its  preceding  joint; 
not  so  strongly  pedicellate  as  with  7.  californicum  and  I.  bromi,  moderately  arched 
above  with  hairs  arranged  in  two  indefinite  whorls;  club  separated  into  two  subequal 
pedicellate  joints,  giving  the  funicle  the  appearance  of  being  6-jointed  instead  of 
5-jointed,  as  with  bromi  and  californicum;  scape  short,  about  as  long  as  pedicel  and 
first  funicle  joint  together;  strongly  expanded  below  tip.  Coloration  like  that  of 
the  female."     (Howard,  Tech.  Ser.  2,  Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  13,  14,  1896.) 

The  earlier  stages  of  development  are  unknown,  hut  they  probably 
differ  little  from  those  of  allied  species.  Quite  likely  the  same  natural 
enemies  prey  upon  it  and  the  same  repressive  measure  will  apply  to  it 
as  with  the  preceding  species. 

WEBSTER'S  ISOSOMA. 

{Isosoma  websteri  Howard.     Fig.  12.) 

This  is  in  all  probability  a  wheat-infesting  species,  as  I  found  it  in 
a  wheat  held  near  Blooming  ton,  111.,  May  9  and  11,  1884:,  and  about 
Lafayette,  Ind.,  also  in  fields  of  wheat,  June  2  and  16,  1885.     I  also 


Pig.  12. — Isosoma  websteri:  adult  female— much  enlarged  (from  Howard). 


reared  it  from  a  pupa  taken  from  a  growing  wheat  plant  in  the 
Bloomington,  111.,  field  May  29,  but  have  not  encountered  it  since 
in  my  studies  of  these  insects.     Nothing  is  known  of  its  life  history 


36 

except  what  I  have  just  given.     Its  close  resemblance  to  I.  maculatum^ 
which  I  have  reared  from  stems  of  cheat  from  the  vicinity  of  Cham 
paign  and    Urbana,  111.,  is  quite  suggestive,  the  adults  of   this  last 
species  being  abroad  during   late  May  and  early  June  in   the  same 
localities. 

DESCRIPTION. 

"Female.- — Length,  3.4  mm.;  expanse  6.3  mm.  Head,  pronotum  and  mesonotum 
as  with  I.  maculatum;  metanotum  with  only  the  beginning  of  a  central  furrow,  its 
lateral  carinse  immediately  curving  around  the  sides,  each  inclosing  an  oval,  flat- 
tened, nearly  smooth  portion  of  the  metascutellum ;  a  median  carina  extending 
nearly  to  the  tip  of  the  sclerite;  pronotal  spot  moderately  large  and  plainly  seen 
from  above,  occupying  a  little  more  than  one-third  of  the  dorsal  aspect  of  the  pro- 
notal f oreborder.  Abdomen  much  longer  than  the  thorax ;  segments  3  to  5  increasing 
in  length;  6  and  7  as  long  as  5.  Antennae  with  joint  1  of  the  funicle  twice  as  long 
as  2;  joints  3,  4,  and  5  gradually  decreasing  in  length,  subequal  in  width;  joint  5 
more  closely  connected  with  club  than  with  the  preceding  joint.  Color  and  wing 
venation  as  with  I.  maculatum."  (Howard,  Tech.  Ser.  2,  Div.  Ent.,  U.  S.  Dept. 
Agr.,  pp.  15,  16,  1896.) 

While,  as  stated,  this  is  probably  a  wheat-infesting  species,  it  is  to 
be  remembered  that  it  has  been  reared  only  in  a  single  instance,  and 
it  is  within  the  range  of  possibility  that  my  growing  wheat  plant,  as  I 
supposed,  might  possibly  have  been  cheat,  as  it  is  easy  to  confuse  the 
young  plants,,  and  as  the  two  grow  everywhere  intermixed  in  the 
fields  mere  collecting  offers  no  solution  of  the  problem  whatever.  Of 
the  four  species  of  Isosoma  which  I  have  reared  from  common  cheat 
(Bromus  secalinus),  viz,  I.  elymi,  I.  albomaculata,  I.  Mrtifrons,  and 
L  maculatum,  none  were  found  in  the  wheat  straws  growing  in  the 
same  field. 

Should  the  species  become  numerous  enough  to  cause  serious  depre- 
dation it  will  probably  yield  to  the  same  repressive  measures  as  the 
other  grain-attacking  forms. 


THE  HAIRY-FACED  ISOSOMA. 

{Isosoma  hirtifrons  Howard.     Fig.  13.) 

The  type  specimens  of  this  species  were  reared  from  rye  straws 
collected  by  Mr.  Coquillett,  in  Mercer  County,  Oal.,  in  1885.  It  was 
reared  by  myself  from  stems  of  common  cheat  growing  in  a  wheat 
field  near  Urbana,  111.,  in  1902.  I  know  nothing  whatever  of  its  life 
history  except  that  it  appeared  in  my  breeding  cages  in  common  with 
the  other  cheat-infesting  species.  The  records  of  the  Illinois  State 
Laboratory  of  Natural  History  and  those  of  the  office  of  the  State 
entomologist  contain  numerous  references  to  Isosoma  attacking  rye. 


37 

Specimens  of  the  affected  straws  show  that  a  part  of  this  injury  was 
duo  to  Isosoma  tritici,  whose  presence  could  be  detected  by  the  larval 
cells  in  the  walls  of  the  straw;  also  many  straws  were  attacked  by  a 
noncell-making  species,  the  larvae  being  in  the  center  of  the  stems 
immediately  above  the  joint.  No  adults  were  reared,  as  the  larvae 
were  supposed  to  be  those  of  the  old  Isosoma  tritici  Riley,  which  is 
not  now  known  to  attack  any  grain  except  wheat.  It  is  therefore 
impossible  to  say  which  of  the  species  whose  larva'  live  in  the  cen- 
ter of  the  stem  it  was  that  did  the  injury  in  these  eases.  I  made 
every  effort  to  secure  material  from  the  fields  of  rye  about  Urbana 
and  Champaign.  111.,  during  the  summer  of  1902,  but  was  unable  to 
find  any  infested  straw,  and  therefore  can  throw  no  light  upon  the 
identity  of  the  rye-attacking  species;  but  the  fact  that  the  one  under 
consideration  is  known  to  affect  rye  in  California  would  place  it  under 


Fig.  13. — Isosoma  hirtifrons  How.:  adult  female,  much  enlarged  (after  Howard  i. 

suspicion  wherever  it  occurs  in  the  eastern  States.  I  judge  that  it 
will  be  very  easily  confused  with  other  species,  and  the  fact  of  its 
infesting  cheat  would  lead  to  the  suspicion  that  it  will  be  found  infest- 
ing other  grasses. 

DESCRIPTION. 


••/•'<  male. — Length,  3.7  mm.;  expanse,  7  mm.  Sculpturing  of  head,  pronotum,  and 
mesonotum  as  in  /.  websteri,  except  that  there  art'  sparse,  large,  .-hallow  punctures  on 
the  mesoscutellum;  cheeks  much  fuller  than  in  other  species;  metanotum  as  with  I. 
maculatum.  Abdomenabout  as  long  as  thorax;  segments  3  to  6  increasing  in  length. 
Antenna-  stout,  moderately  long,  very  hairy;  proportions  about  as  in  /.  websU  ri.  Body 
not  unusually  pilose,  except  face,  which  is  closely  covered  with  short  white  pile;  pro- 
notal  spots  very  plain,  but  not  large,  occupying  about  one-third  of  the  dorsal  aspect 
of  the  fore-border  of  the  pronotum.  Color  black,  except  for  all  femoro-tibial  knees 
and  pronotal  spot.  Claw  of  stigmal  club  given  off  some  distance  from  tip.  delicate 
and  short."      (Howard,  Tech.  Ser.  2,  Div.  Ent,  V .  S.  Dept.  Agr.,  p.  16,  1896.  | 


38 

Up  to  the  present  time  cheat  has  been  looked  upon  only  as  an 
undesirable  plant  growing  among  wheat  like  weeds  among  corn,  but 
it  now  appears  to  be  doubly  undesirable  on  account  of  its  harboring 
insect  enemies  of  cultivated  grains. 


ISOSOMA  SECALE  Fitch. 

This  was  described  by  Doctor  Fitch  in  1861,  after  he  had  become  fully 
convinced  that  these  insects  were  not  parasitic  but  the  true  depredators 
among  grain. a  I  have  not  myself  encountered  it  in  the  study  of  grain 
insects,  but  from  the  statements  of  Doctor  Fitch  it  does  not  seem  to  differ 
in  habits  from  Isosoma  hordei  and  I.  tritici,  and  one  can  not  help  sus- 
pecting that  a  careful  study  of  its  life  history  and  development  will 
show  that  it  is  one  of  these  species.  It  was  given  the  common  name 
of  urye  fly,"  and  adults  were  reared  from  straws  grown  in  1860, 
emerging  about  the  1st  of  June,  1861.  The  larvae  were  found  to 
occupy  cells  in  the  walls  of  the  rye  straw,  and  not  in  the  base  of  the 
sheaths,  as  was  supposed  to  be  the  case  with  I.  hordei,  though  Doctor 
Fitch  describes  "the  disease  which  the  insect  causes  in  the  rye  being 
in  every  particular  like  that  in  barley  and  wheat."  As  we  now  know, 
barley  and  "wheat  are  attacked  by  two  different  species,  but  all  three 
seem  to  have  precisely  the  same  life  history,  so  that  whether  there  be 
one  species  or  more,  the  farmer  will  be  able  to  meet  it  or  them  with 
the  same  preventive  measures. 

DESCRIPTION. 

"Female. — Length,  3.6  mm.;  expanse,  6.6  mm.  Punctation  as  with  I.  hordei;  pro- 
notal  spot  large,  plainly  seen  from  above.  Abdomen  as  long  as  head  and  thorax; 
segments  4  and  5  subequal;  6  and  7  together  shorter  than  5;  2  much  longer  than  4 
and  5  together.  Color  black;  scape  and  legs  black;  front  tibiae,  knees,  and  tips  of 
middle  and  hind  tibiae  and  all  tarsi  honey  yellow;  claw  of  stigmal  club  given  off  near 
tip  of  club,  somewhat  curved;  antennae  as  in  I.  hordei. 

"Male.- — Length,  3  mm. ;  expanse,  5  mm.  Specimen  in  poor  condition.  Expansion 
of  scape  more  abrupt  from  tip  than  with  other  males  described;  funicle  joints  well 
arched  above,  scarcely  pedicellate,  each  with  2  indefinite  whorls  of  hair  and  with  no 
median  constriction;  each  joint  twice  as  long  as  wide;  club  plainly  divided  into  two 
joints,  but  no  trace  of  pedicel  to  terminal  joint,  resembling  I.  hordei  in  this  respect; 
petiole  a  little  shorter  than  hind  coxae  and  shorter  than  first  abdominal  segment." 
(Howard,  Tech.  Ser.  2,  Div.  Ent.,  U.  S.  Dept.  Agr.,  p.  19,  1896.) 

In  this  connection  it  may  not  be  out  of  place  to  state  that  I  have 
reared  an  undetermined  species  of  Isosoma  in  connection  with  I.  hor- 
dei from  the  stems  of  Elymus  canadensis,  growing  near  Champaign, 
111.,  and  seeming  to  affect  the  grass  much  in  the  same  manner  as 

«  Seventh  Report  Noxious  and  other  Insects  of  New  York,  pp.  849-851. 


39 

that  species.  It  may  on  further  study  prove  to  have  some  connection 
with  the  one  now  being"  discussed,  though  I  have  not  found  it  attack- 
ing rye. 

FITCH'S    ISOSOMA. 

( Isosoma  filch  ii  II o ward. ) 

This  is  the  last  of  the  described  Isosomas  known  to  attack  growing 
grain,  though  1  have  reared  what  appears  to  be  still  another  from 
wheat  straws  from  Carbondale,  111.;  but  the  specimens  are  still 
undetermined  and  nothing  definite  can  now  be  said  of  them.  This 
species  was  described  from  2  females  and  1  male  found  in  the  Fitch 
collection,  labeled  in  Fitch's  handwriting,  "  Eur  y  torn  a  hordel  Harris, 
Nos.  15223  and  15197."  Nothing  whatever  is  known  of  its  habits, 
but  it  was  presumably  reared,  with  some  other  species,  from  grain. 

DESCRIPTION. 

" Female. — Length,  3  mm.;  expanse,  5.8  mm.  Head,  pronotum,  and  mesonotum 
faintly  shagreened,  nearly  smooth,  shining;  mesoscutellum  with  a  few  sparse  punc- 
tures; metanotum  with  a  complete  median  longitudinal  furrow  emarginate  on  the 
anterior  half  and  with  a  central  carina  extending  nearly  to  tip;  very  coarsely  rugu- 
lose  either  side  of  the  furrow  with  a  faint  granulation  between  raised  lines;  pronotal 
spot  large,  plainly  seen  from  above,  and  two  spots  together  occupying  about  one- 
third  of  the  dorsal  aspect  of  the  foreborder  of  the  pronotum.  Antenna?  with  well- 
separated  joints;  funicle  joints  2,  3,  4,  and  5  equal  in  length  and  width;  joint  1  a 
little  longer;  joint  5  as  well  separated  from  the  club  as  from  preceding  joint;  club  a 
little  longer  than  4  and  5  together,  but  of  the  same  width.  Abdomen  as  long  as  the 
thorax;  joint  4  shorter  than  6;  5  longer  than  6;  7  and  8  subequal.  Color  black, 
except  for  pronotal  spot  and  knees,  which  are  luteous;  claw  of  stigmal  club  given  off 
about  at  tip  of  club,  straight. 

"Male. — Length,  2.2  mm.;  expanse,  4.2  mm.  Petiole  about  as  long  as  hind  coxse 
and  nearly  equal  in  length  to  first  abdominal  segment.  Antennae  with  funicle  joints 
very  slightly  arched  above,  each  joint  fully  three  times  as  long  as  wide,  and  slightly 
constricted  in  the  middle;  otherwise  as  with  /.  Jiordci."  (Howard,  Tech.  Ser.  2. 
Div.  Ent.,  U.  S.  Dept.  Agr.,  p.  20,  1896.) 

I  have  now  treated  all  of  the  species  of  these  insects  known  to  attack 
cultivated  grains  in  this  country,  though  there  may  be  still  others  as 
yet  unknown.  These  known  species  have  been  described  in  each  case, 
not  especially  for  the  benefit  of  the  unentomological  farmer  but  because 
this  publication  will  go  to  many  lands  and  into  the  hands  of  many  dif- 
ferent peoples.  Some  will  care1  nothing  for  descriptive  matter,  and 
such  can  easih^  pass  over  it  in  the  use  of  this  bulletin,  but  there  will 
be  others  who  will  look  to  its  pages  for  aid  in  determining  with  exact- 
ness the  identity  of  the  species  which  they  may  have  before  them,  and 
for  these  descriptions  are  a  necessity.  Some  of  the  species  included 
may  appear  to  be  of  no  especial  interest  to  the  practical  farmer,  but 
of  this  no  one  can  confidently  predict.     It  may  be  true  to-day  and  not 


40 

true  to-morrow,  for  no  one  can  tell  what  year  or  in  what  part  of  the 
country  any  one  of  these,  even  the  one  that  seems  the  most  insignifi- 
cant, may  suddenly  come  to  the  front  and  commit  serious  depredations 
over  a  considerable  area.  Besides  this,  they  are  all  of  them  so  obscure 
in  appearance  and  their  effect  on  the  plants  they  attack  so  subtile  and 
hidden  from  the  eyes  of  the  farmer  that  he  is  unaware  of  his  loss  until 
on  threshing  his  grain  he  finds  that  it  does  not  turn  out  well  and  the 
kernels  are  light  and  shriveled.  It  is  like  the  thefts  of  a  trusted  offi- 
cial— they  are  not  missed  until,  by  accident,  perhaps,  the  defalcations 
are  discovered,  when  we  are  struck  with  amazement  at  their  magni- 
tude and  ask  ourselves  and  each  other  how  it  is  possible  for  such 
things  to  go  on  continually  through  a  long  series  of  years  and  escape 
detection.  The  financial  loss  occasioned  by  an  unusually  disastrous 
outbreak  of  these  pests  can  be  estimated,  but  it  is  a  mistake  to  sup- 
pose that  such  losses  constitute  more  than  a  very  small  percentage  of 
the  amount  annually  filched  from  the  farmers  by  these  insidious  foes 
of  his  crops.  It  is  not  so  much  the  big  losses  that  occur  at  rare  inter- 
vals, and  of  which  we  read  much  in  the  public  press,  but  the  infinite  and 
perpetual  leaks  from  this  source  that  pull  down  the  farmer's  profits — 
leaks  that,  as  has  been  shown,  he  may  readily  prevent  in  a  most  inex- 
pensive manner.  It  is  for  the  very  reason  of  their  obscurity  and 
insidious  attacks,  coupled  with  the  magnitude  of  the  losses  caused  by 
them  through  a  long  series  of  years,  that  has  prompted  a  study  of 
their  habits  and  the  publication  of  the  facts  in  the  present  form. 

THE  TWO-WINGED  GRAIN  AND  GRASS  FLIES. 

The  insects  included  under  this  head  are  true  flies,  having  only  two 
wings  and  their  young  are  maggots  without  feet,  eyes,  or  jaws.  They 
belong  to  the  family  Oscinidee,  containing  a  large  number  of  species 
with  variable  food  habits,  some  of  them  not  attacking  plants,  but  living 
on  the  cast  skins  of  other  insects,  shells  of  insect  eggs,  and  in  the  bur- 
rows made  in  plants  by  other  insects.  Some  of  them  are  leaf-miners, 
others  live  in  galls  on  grasses,  while  still  others  live  underground  on 
the  roots  of  plants.  Still  others,  that  are  known  to  live  in  the  stems 
of  grain  and  cause  more  or  less  destruction  by  their  attacks,  will  be 
here  considered,  though  it  must  not  be  supposed  that  there  are  not 
still  others  of  such  depredators  of  which  we  as  yet  know  nothing. 

Our  grain-affecting  species  are  to  be  found  in  the  genera  Meromyza, 
Chlorops,  Elachiptera,  and  Oscinis.  It  is  to  the  last  that  the  very 
destructive  frit-fly  {Oscinis  frit)  of  England  and  Europe  belongs  and 
which  is  so  terribly  destructive  to  grain  crops  in  those  countries.  The 
habits  of  Meromyza  americana  have  been  pretty  well  studied  and  we 
now  have  a  fairly  good  knowledge  of  its  life  history  and  habits;  but  of 
the  most  of  the  other  species  belonging  to  the  above  genera  we  only 


41 

know  that  they  attack  the  stems  of  wheat  and  other  smaller  grains,  hut 
we  are  far  from  possessing  a  full  knowledge  of  their  life  cycles. 
Chlorops  proximo,  Say  is  known  to  attack  wheat  plants  in  Kentucky, 
flies  emerging  in  May;  I  have  reared  Elachiptera  longuia  Loew  f rom 
maggots  in  the  stems  of  Panicum  criis-galli  in  Illinois,  the  flies  in  this 
case  appearing  late  in  August,  and  from  both  wheat  and  out  plants  in 
Indiana.  It  has  also  been  reared  from  oats  in  Ohio  by  Prof.  W.  B. 
Alwood.  From  wheat  plants  in  Indiana  I  have  reared  Elachiptera 
nigricornis  Loew,  and  from  the  same  lot  of  plants  I  reared  also  E.  costata 
Loew,  the  latter  having  been  reared  from  oats  in  Ohio  by  Professor 
Alwood  and  from  maggots  found  in  a  decayed  cavity  in  the  roots  of 
living  garden  radish  in  Illinois  by  Mr.  Coquillett.  The  extent  to  which 
the  larvae  of  the  last  species  attacks  and  destroys  wheat  plants  is  uncer- 
tain, for  though  I  have  reared  them  from  volunteer  wheat  plants  grow- 
ing up  in  the  fields  I  have  never  been  able  to  separate  their  maggots 
from  those  of  Oscinis.  I  have  reared  Oscinis  trigramma  Loew  and  0. 
coxendix  Fitch  from  volunteer  wheat  plants  in  Indiana,  and  O.  dorsata 
Loew,  0.  coxendix  Fitch,  0.  umbrosa  Loew.  and  0.  trigramma  Loew 
from  August-sown  wheat  at  Wooster,  Ohio.  Oscinis  carbonaria  Loew 
is  treated  in  this  paper  under  the  head  of  the  lesser  wheat-stem  maggot. 
The  larvae  of  all  of  these  except  Meromyza  closely  resemble  each  other, 
work  in  the  }Toung  plants,  and,  some  of  them  at  least,  destroy  the  cen- 
tral stem  before  the  plant  tillers  or  individual  tillers  afterwards.  The 
larvae  or  maggots  are  small,  yellowish  white,  pointed  anteriorly,  but 
more  blunt  at  posterior  extremity,  without  jaws,  but  provided  with  a 
pair  of  minute  hooks  whereby  they  rend  the  tender  growth  of  the  plant 
and  extract  the  juices.  They  may  generally  be  found  in  the  midst  of 
their  work  surrounded  by  the  injured  tissue  and  grass  saturated  with 
the  sap  of  the  plant,  and  later  on  the  brown  puparia  may  be  observed 
about  the  bases  of  the  young  plants  in  late  fall  and  even  outside  the 
sheaths,  and  scattered  on  the  ground  in  spring.  The}T  are  often  mis- 
taken by  farmers  for  the  "flaxseed"  or  corresponding  stage  of  the 
Hessian  fly. 

WERE    PROBABLY    ORIGINALLY    GRASS    FEEDERS. 

Beyond  a  doubt  the  larvae  of  these  flies  were  originally  grass  feed- 
ing, and  we  find  them  at  present  developing  in  the  stems  of  grass,  but 
seemingly  preferring  grain  at  times,  probably  when  the  grain  at  the 
time  of  oviposition  offers  a  more  inviting  place  for  the  female  to 
deposit  her  eggs  with  the  assurance  that  her  offspring  will  be  within 
reach  of  an  ample  supply  of  food.  LTntil  the  last  half  of  the  last  cen- 
tury the  average  farmer  paid  little  attention  to  such  matters,  and,  as 
the  flies  were  as  now  less  thoroughly  studied  than  other  insects,  there 
was  little  to  encourage  the  entomologist  in  attempting  to  study  their 
habits,  as  it  is  rather  a  thankless  task  to  rear  them  and  get  their  life 


42 

history  worked  out  only  to  learn  that  the  species  can  not  be  deter- 
mined, and  the  information  thus  gained  is  thus  rendered  practically 
worthless  because  of  not  being  able  to  state  definitely  which  of  the 
many  forms  one  has  been  studying.  Only  recently  I  have  learned 
the  name  of  a  species  reared  from  grass  stems  eighteen  years  ago. 
For  this  reason  even  now  the  earlier  stages  of  nearly  all  of  those  reared 
from  growing  grain  are  obscure  or  unknown,  the  flies  having  simply 
been  reared  from  grain  or  grass,  but  the  young  of  any  particular 
species  can  not  be  separated  from  those  of  perhaps  a  half  dozen  other 
similar  flies.  There  is  much  need  at  present  of  careful  studies  of 
these  insects  with  a  view  of  determining  their  exact  relation  to  agri- 
culture, and  especially  to  what  extent  they  may  be  combated  outside 
the  grain  fields  of  the  farmer.  At  present  not  more  than  one  farmer 
out  of  a  thousand  knows  of  their  existence,  and  the  injuiy  they  do  is 
attributed  to  the  Hessian  fly,  thus  to  a  certain  degree  throwing 
obscurity  over  all  reports  of  the  ravages  of  the  latter  insect,  which 
can  not  be  reached  outside  the  grain  field,  while  some  at  least  of  these 
other  flies  surely  can.  When  I  began  to  study  the  life  history  of  the 
lesser  wheat- stem  maggot,  in  1884,  it  was  the  most  unsatisfactory 
and,  at  that  time,  to  all  appearances,  the  most  unprofitable  piece  of 
work  that  I  ever  undertook,  for  the  reason  that  it  was  impossible  to 
separate  it  from  other  similar  species;  but  this  has  now  been  largely 
overcome  with  this  insect,  and  we  know  that  much  can  be  done  to 
prevent  its  injuries. 

EARLY   REPORTS   OF   INJURIES   TO   GRAIN. 

One  of  the  earliest  reports  of  injuries  to  grain  in  this  country  that 
can  be  attributed  to  these  insects  with  any  degree  of  certainty  was 
cited  by  A.  S.  Fuller,  from  the  works  of  M.  Du  Hamel  du  Menceau 
(New  Hamburg  edition  of  1759),  as  follows: 

There  is  a  smaller  kind  of  worm  which  gets  into  the  roots,  chiefly  oats,  and  work- 
ing upward  destroys  all  the  inside  of  the  plant,  which  perishes  soon  after.  I  sus- 
pect it  to  have  been  an  insect  of  this  kind  that  destroyed  so  much  wheat  in  the 
neighborhood  of  Geneva,  and  which  M.  de  Chateau vieux  described  thus:  "Our 
wheat  in  the  month  of  May,  1755,  sustained  a  loss  which  even  that  cultivated  accord- 
ing to  the  new  husbandry  did  not  escape.  We  found  in  it  many  little  white  worms, 
which  afterwards  became  a  chestnut  color.  They  post  themselves  between  the 
blades  and  eat  the  stems.  They  are  usually  found  between  the  first  joint  and  the 
roots.  Every  stalk  which  they  attacked  grew  no  more,  but  became  yellow  and 
withered.  The  same  misfortune  happened  to  us  in  the  year  1732.  These  insects 
appeared  about  the  middle  of  May  and  made  such  havoc  that  the  crop  was  almost 
destroyed. ' ' 

The  attack  on  oats  was  clearly  that  of  the  stalk  borer  or  heart  worm, 
the  caterpillar  of  the  moth  Papaipema  ( Gortyna)  nitela  Guen. ,  but 
that  in  the  wheat  does  not  accord  with  the  work  of  any  other  than  of 
some  of  these  small  grain  and  grass  flies  under  consideration.     Mero- 


43 

rayza  maggots  do  not  turn  brown  or  "chestnut  colored,"  and  those  of 
the  Hessian  fly,  even  if  it  were  known  to  occur  in  America  at  that 
early  date,  do  not  eat  off  the  stems.  As  early  as  1^22  Mr.  James 
Worth,  of  Bucks  County,  Pa.,  seems  to  have  reared  these  flies  from 
maggots  attacking  wheat. 

It  is  therefore  probable  that  as  the  area  of  cultivation  increased 
in  this  country  these  insects  have  gradually  transferred  their  atten- 
tion from  grass  to  grain  as  a  matter  of  necessity,  and  though  more  or 
less  numerous  every  year  in  the  grain  fields,  they  become  excessively 
so  when  the  grass  conditions  are  less  favorable  than  those  of  the  grain; 
but  the  grasses  are  a  continual  source  of  supply  from  which  the  grain 
fields  are  colonized.  These  interrelations  may  be  more  or  less  cur- 
tailed by  fhe  farmer  with  but  little  expense. 

THE  GREATER  WHEAT  STEM-MAGGOT. 
{Meromyza  amerwana  Fitch.     Fig.  14.) 

PAST   HISTORY   OF   THE    INSECT. 

This  is  in  all  probability  an  insect  native  to  the  far  South,  as  it 
occurs  in  Mexico  and  northward  over  the  entire  United  States  and  far 
into  British  America,  its  food  plants,  before  the  advent  of  the  Cau- 
casian farmer,  being  the  wild  grasses.  The  fly  was  described  in  1856 
under  the  name  here  applied,  but  without  definite  proof  of  its  attack- 
ing grain  further  than  that  it  was  collected  in  wheat  fields  and  closely 
resembled  the  European  species  Meromyza  saltatrix  Linn.  There  is 
now,  however,  considerable  evidence  of  its  having  attacked  growing- 
wheat  at  least  as  early  as  1822  in  Pennsylvania  a  and  in  1845  in  Michi- 
gan. b  The  evidence  furnished  by  Mr.  James  Worth,  of  Bucks  County, 
Pa.,  indicates  that  three  broods  were  observed,  as  he  calls  attention  to 
the  attacks  of  "a  little  worm  found  in  the  lower  part  of  the  stalks  of 
wheat  and  rye  in  spring  and  fall  and  about  the  joints  in  June."  Of 
these  larvae  he  says  that  "some  were  pale  yellow,  with  brown  spots 
about  the  mouth,"  which  would  imply  that  they  were  those  of  some 
species  of  Isosoma;  but  he  further  states  that  one  kind  was  found  in 
volunteer  wheat,  which  the  Isosomas  do  not  attack,  and  their  larvae 
are  not  found  in  the  plants  in  fall,  and  in  case  of  only  one,  with  a 
possibility  of  another  species,  are  they  to  be  found  in  the  plants  in 
spring.  While  Mr.  Worth  evidently  was  not  able  to  separate  the 
different  species  of  the  larvae  found  in  growing  grain,  his  careful 
descriptions  and  exactness  in  locality  and  dates  are  exceedingly  val- 
uable and  enable  those  familiar  with  the  forms  of  which  he  writes  to 
recognize  them  with  reasonable  clearness.  Hence  we  are  left  with 
little  doubt  that  he  observed  the  larvae  of  Isosoma  and  Meromyza 

«The  American  Farmer,  vol.  4,  p.  394;  Memoirs  Perm.  Agl.  Soc.,  Vol.  1,  p.  165. 
t> Prairie  Farmer,  Sept.,  1845,  p.  216. 


44 


without  separating  them,  and  also  in  fall,  including  those  found  in 
volunteer  wheat,  this  latter  species  and  other  Oscinidee.  The  reference 
in  the  Prairie  Farmer  seems  to  have  been  drawn  out  by  a  notice  in  the 
Michigan  Farmer  of  a  new  wheat  insect  in  that  State,  described  as  the 
product  of  a  greenish  fly  about  three-sixteenths  of  an  inch  in  length, 
whose  larva  is  a  white  worm  one-fourth  of  an  inch  long,  ribbed,  without 
feet,  with  two  forked  lines  on  its  forehead,  found  in  the  straw  above 
the  upper  joint,  where  it  devours  the  juices  which  would  otherwise 
ascend  to  the  head,  but  which  denote  the  presence  of  the  worm  in  the 
straw  by  turning  white  prematurely  when  the  grain  is  in  the  milk. 
There  is  also  here  reference  to  the  presence  of  u9  eggs  *  *  'J 
found  in  a  single  straw,  one  of  which  had  just  hatched,"  but  which 
eggs,  so  called,  are  now  known  to  have  been  the  bodies  or"  a  minute 

parasitic  mite,  whose 
rounded  form  is  not  unlike 
that  of  an  egg  and  which 
is  occasionally  found 
attacking  the  maggot  in 
the  straws. 

Doctor  Fitch  did  not 
rear  the  flies  which  he 
described,  but  collected 
this  in  connection  with 
several  species  of  Oscinis 
by  sweeping  in  the  wheat 
fields  with  an  insect  net. 
Being  familiar  with  the 
grain  attacking  habits  of 
similar  insects  in  Europe, 
he  expected,  as  he  says,  to 
rear  the  flies  from  the 
growing  wheat  plants  at 
different  seasons,  but  fail- 
ing, as  he  states,  to  do  this,  contented  himself  with  describing  the  flies 
without  attempting  to  connect  them  with  the  injuries  which  he  clearly 
observed.  Nothing  further  appears  to  have  transpired  relative  to  this 
insect  until  in  the  year  1867,  when  Doctor  Riley  reared  the  fly  from 
larvae  working  in  the  growing  stems  of  wheat,  immediately  above  the 
upper  joint,  in  the  month  of  June,  and  in  Missouri.  In  this  case  the 
flies  appeared  during  the  first  week  of  July,  after  a  pupal  period  of 
twelve  to  fourteen  days.  These  facts  were  published  in  the  Rural  New 
Yorker  for  January  28,  1869,  and  in  his  first  report  as  State  entomol- 
ogist of  Missouri  he  discussed  the  insect  and  gave  illustrations  of  the 
adult,  larval,  and  pupal  stages,  but  does  not  appear  to  have  suspected 
the  occurrence  of  a  second  brood  later  in  the  season.  In  1876  a  farmer 
of  Hinckley,  Ohio,  reported  it  as  attacking  his  spring  wheat. a     We 


Fig.  14. — Greater  wheat  stem-maggot  {Meromyza  americana); 
a,  mature  fly;  b,  larva;  c,  puparium;  d,  infested  wheat  stem — 
all  enlarged  except  d  (from  Marlatt). 


a  Country  Gentleman,  July  27,  1879. 


45 

also  hear  of  it  during'  this  same  year  in  the  State  of  New  York,  where 
stalks  of  growing  wheat  containing  the  larva'  were  sent  to  Doctor  Lint- 
ner,  from  Seipioville.  in  August.  Some  of  these  stalks  contained 
larvae  and  some  of  the  flies  were  observed  crawling  about  on  the  table 
where  the  package  had  been  unwrapped,  and  these  were  supposed  to 
have  emerged  from  the  straws  while  in  transit.  Doctor  Lintner  adds 
nothing  to  our  knowledge  of  the  species  at  this  time,  but  gave1  it  the 
common  name  of  the  wheat  stem-maggot  in  preference  to  Doctor 
Fitch's  American  Meromyza.a 

In  March,  1883,  Dr.  S.  A.  Forbes,  State  entomologist  of  Illinois, 
received  information  of  serious  injuries  to  young  wheat  in  Fulton 
County,  of  thpt  State,  and  on  investigation  found  the  depredator  to  be 
a  small,  slender  maggot  which  attacked  the  plant  just  above  the  root, 
thereby  killing  it.  Farmers  in  the  infested  territory  had  noticed  the 
injury  during  the  preceding  November  and  December,  but  had  not 
taken  steps  to  learn  of  its  destructive  character  until,  with  the  coming 
of  spring,  the  pest  seemed  to  break  out  anew.  From  larvae  taken  from 
infested  plants  from  these  fields  puparia  were  obtained  April  30,  and 
the  flies  began  to  appear  by  May  4,  and  continued  to  emerge  until 
June  1,  thus  showing  that  the  insect  might  do  serious  damage  to  young 
wheat  in  the  fall,  pass  the  winter  in  the  maggot  stage,  and  resume  its 
work  of  destruction  again  in  spring.  This,  taken  in  connection  with 
what  had  been  observed  by  Riley  and  Lintner,  showed  plainly  that  the 
flies  emerging  in  May  and  June  oviposited  in  the  growing  stems  of 
the  wheat,  and  the  larvae  hatching  from  these  eggs  entered  the  stems 
just  above  the  upper  joint.  Doctor  Forbes,  in  his  thirteenth  report  as 
State  entomologist,  gave  full  details  of  his  observations  and  called 
attention  to  the  possibility  of  a  third  brood  developing  in  midsummer, 
and  also  gave  the  insect  the  common  name  of  the  "  wheat-bulb  worm."* 

During  the  summer  of  1884  I  was  engaged  as  a  special  agent  of  the 
Division  of  Entomology,  under  Doctor  Riley,  and  from  June  1  to  Octo- 
ber was  located  at  Oxford,  Ind.,  engaged  in  the  study  of  grain  insects, 
especially  those  attacking  wheat.  From  straws  taken  from  a  field  near 
Oxford  I  reared  adult  flies  up  to  Jul}T  26,  and  volunteer  wheat,  taken 
from  this  same  field  September  5  and  sent  to  Washington,  gave  adults 
September  11,  13,  and  16,  according  to  the  divisional  notes.  During 
the  same  year  adults  were  reared  from  volunteer  wheat  October  1  and 
found  in  the  field  of  young  wheat  on  October  6/  In  1886  Doctor 
Forbes  put  the  final  touch,  so  to  speak,  to  the  settlement  of  the  occur- 
rence of  this  midsummer  brood  by  finding  both  eggs  and  larva4  on 
August  4  in  volunteer  wheat,  and  in  his  fifteenth  report  (p.  39)  con- 
structed a  calendar  showing  the  periods  covered  by  the  several  broods. 

«Loc.  cit.,  Vol.  XLIY,  p.  535,  1879. 

b  13th  Kept,  State  Entomologist  of  Illinois,  pp.  13-29,  1884. 

cRept.  U.  S.  Comm.  Agr.,  1884,  p.  390;  Bull.  9,  Purdue  Univ.,  Oct.,  1886. 


46 

This  calendar  shows  our  combined  work  on  the  insect,  and  is  all  the 
more  valuable  on  account  of  our  having  worked  entirely  independently 
of  each  other  over  territory  within  the  same  latitude,  and  with  other 
conditions  in  every  way  similar.  It  is  also  a  matter  of  interest  that 
on  February  27,  1891,  I  collected  all  stages  of  the  insect  except  the 
eggs  in  wheat  growing  on  the  grounds  of  the  Agricultural  College  of 
Texas,  at  College  Station. 

LIFE    HISTORY. 

Throughout  the  region  of  latitude  40°  N.  the  insect  is  three- brooded, 
although  there  may  be  but  two  in  the  north  and  more  than  three  in  the 
far  south,  though  Doctor  Fletcher  states  that  about  Ottawa,  Canada, 
about  latitude  45°  N.,  there  are  three  broods,  the  adults  appearing  in 
the  beginning  of  June,  the  end  of  July,  and  again  late  in  September. 
My  observation  in  Texas,  about  latitude  30°  30',  does  not  necessarily 
indicate  additional  broods,  as  there  may  be,  as  with  the  Hessian  fly,  a 
prolonged  summer  resting  period,  during  which  the  insect  is  continued 
in  a  stage  requiring  no  food  and  incapable  of  reproduction,  until  the 
vegetation  upon  which  the  larvae  are  dependent  for  their  food  supply 
begins  to  take  on  new  life,  and,  as  with  the  Hessian  fly,  we  may  find 
that  the  very  conditions  that  serve  to  prevent  the  starting  up  of  the 
fresh  growth  of  vegetation,  so  essential  to  the  life  of  the  young  larvae, 
has  also  the  effect  of  retarding  the  emerging  of  the  parent  insects.  Such 
problems  as  these  are  for  National  investigation,  where  imaginary 
lines  and  political  boundaries  do  not  enter  into  consideration.  Within 
the  wheat  belt  of  the  United  States,  broadly  speaking,  the  life  cycle  of 
this  insect  is  as  follows:  The  winter  is  passed  in  the  larval  stage,  and 
the  short  pupal  stage  coming  in  May  brings  the  emerging  of  the  adults 
at  the  time  when  the  female  is  able  to  place  her  eggs  on  the  plants 
where  the  young,  on  hatching,  will  make  their  way  to  the  tender  and 
succulent  stem  just  above  the  upper  joint.  By  the  time  the  straw  has 
ripened  the  larvae  have  ceased  to  require  food,  and  pass  through  the 
pupal  stage,  the  adults  of  this  brood  appearing  in  July.  Eggs  are  now 
deposited  in  volunteer  wheat  and  grass,  and,  owing  either  to  the  retard- 
ing effects  of  meteorological  influences  or  a  diversity  of  food  of  the  larvae 
or  both,  perhaps,  the  emerging  of  the  adults  is  prolonged  throughout 
a  period  extending  from  late  August  through  September  until  late 
October.  At  this  period  the  fall  wheat  offers  a  decidedly  inviting 
plant  to  the  female  fly  on  which  to  place  her  eggs  with  a  prospect  of 
her  progeny  having  an  abundant  food  supply.  It  is  the  larvae  from 
eggs  deposited  during  this  period  that  winter  over  in  the  plants  and 
give  rise  to  the  May -June  generation  of  flies.  It  is  this  last  brood  that 
is  of  more  especial  interest  to  the  farmer,  as  it  is  very  seldom  that  the 
pest  does  serious  injury  to  grain  except  in  fall  and  early  spring. 


47 

DESCRIPTION. 

Adult. — Length,  0.17  inch  to  tip  of  abdomen  and  0.20  inch  to  end  of  wings. 
Color,  yellowish  white,  with  a  black  spot  on  the  top  of  the  head,  which  is  con- 
tinned  backward  to  the  pedicel  of  the  neck.  Thorax  with  three  black  stripes, 
approaching  each  other  anteriorly,  but  not  coming  in  contact,  the  middle  stripe  pro- 
longed anteriorly  to  the  pedicel  of  the  neck  and  posteriorly  to  the  apex  of  the 
scutel.  Abdomen  with  three  broad,  blackish  stripes,  which  arc  confluent  posteriorly 
and  interrupted  at  each  of  the  sutures.  Tips  of  the  feet  and  veins  of  the  hyaline 
wings  blackish.    Eyes,  bright  green.    Antennae,  dusky  on  their  upper  side.    ( Lintner.) 

Egg. — Snow  white,  fusiform,  longitudinally  ridged,  the  space  between  the  ridges 
being  concave  and  marked  off  into  rectangular  areas  by  still  slighter  ridges  transverse 
to  the  others.     Length,  0.023  inch;  breadth,  0.005  inch.      (Forbes.) 

Larva. — Very  pale  green,  slender,  footless,  tapering  anteriorly,  somewhat  nar- 
rowed, but  subtruncate  posteriorly ;  one-fourth  of  an  inch  in  length  by  about  one- 
eighth  of  an  inch  in  width.  The  segments  are  thirteen  in  number,  including  the 
head,  those  in  the  center  of  the  body  being  a  little  wider  than  long.  The  four  ante- 
rior segments  narrow  rapidly  forward,  the  one  next  the  head  being  at  its  apex  less 
than  half  the  diameter  of  the  fourth.  The  three  posterior  segments  are  also  some- 
what narrowed,  the  penultimate  being. about  three-fourths  the  diameter  of  the  sec- 
ond preceding.  The  head  is  provided  beneath  with  the  pair  of  black  toothed  hooks 
common  to  many  dipterous  maggots.  The  antennae  are  very  short,  scarcely  longer 
than  broad,  two-jointed,  the  second  joint  extensile.  There  are  two  circular,  appar- 
ently sensory,  areas  below  the  antenme  upon  the  front  of  the  head,  doubtless  repre- 
senting maxillary  palpi.  The  mouth  is  beneath  the  head,  sucker-like  in  form.  The 
last  or  anal  segment  is  divided  into  two  lobes  and  bears  upon  its  posterior  surface 
two  breathing  pores  or  spiracles,  each  guarded  by  a  circlet  of  about  twelve  depressed 
spines.  The  surface  of  the  larva  is  entirely  smooth  and  shining,  except  for  some 
very  fine  transverse  ridges  on  the  under  side  of  the  segment^,  evidently  used  in  loco- 
motion. On  each  side  of  the  base  of  the  second  segment  is  a  small,  gill-like  append- 
age, divided  into  two  lobes,  each  lobe  with  six  divisions.     (Forbes.) 

Pupa. — The  pupa  of  this  species  is  what  is  technically  known  as  a  coarctate  pupa, 
contained  within  the  last  skin  of  the  larva,  which  is  not  shed  previous  to  transfor- 
mation, but  remains  as  a  protective  envelope  for  the  forming  pupa.  As  the  latter 
shows  through  its  case,  the  color  is  green,  except  at  the  ends,  where,  with  the  growth 
of  the  pupa  within,  the  case  is  left  empty  and  transparent.  It  is  about  one-sixth 
of  an  inch  long  by  one-fifth  in  width,  and  divided  into  ten  clearly  recognizable 
segments.  The  anterior  of  these,  corresponding  to  the  head  and  first  segment  of 
the  larva,  is  yellowish,  shrunken,  and  corrugated,  about  half  the  width  of  the  third 
segment.  The  second  and  third  are  obscurely  divided,  the  first  being  short  and 
narrowing  rapidly  forward.  Within  it  are  observed  the  retracted  maxillae  of  the  old 
larva.  The  remaining  segments  to  the.  eighth  are  about  equal  in  length,  separated  by 
deeply  impressed  sutures  at  first,  the  anterior  sutures  becoming  obliterated  as  the 
enlargement  of  the  head  and  thorax  of  the  pupa  within  distends  the  envelope.  The 
ninth  segment  is  the  longest  of  all,  the  tenth  being  nearly  equally  long,  but  narrower, 
and  shrunken  and  wrinkled  on  its  posterior  border.  The  eleventh,  representing  the 
twelfth  of  the  larva,  is  only  a  brown  and  corrugated  rudiment.  As  the  development 
of  the  pupa  approaches  completion,  the  eyes,  wing-pads,  and  legs  are  visible  through 
the  transparent  covering,  but  they  form  no  elevations  of  the  surface.      (Forbes.) 

FOOD   PLANTS. 

Besides  wheat,  rye,  oats,  and  barley,  all  of  which  it  has  long-  been 
known  to  infest,  I  have  reared  Meromyza  americana  from  the  com- 


48 

mon  bluegrass  {Poa  pratensis) ,  while  Doctor  Fletcher,  in  Canada,  has 
reared  the  flies  from  maggots  in  the  stems  of  Agropyron,  Deschampsia, 
Elymus,  and  Poa,  and  as  he  states  that  the  flies  are  enormously  abun- 
dant in  meadows  and  prairies  all  the  way  from  northern  Quebec 
through  the  Lake  Superior  region,  Manitoba,  and  the  Northwest  Ter- 
ritories, there  seems  to  be  ample  proof  of  its  ability^  to  sustain  itself 
without  trouble  among  the  grasses  of  that  country. 

The  extent  to  which  it  attacks  fall  wheat  in  autumn  is  entirely 
obscured  from  the  fact  that,  in  the  majority  of  cases,  it  is  confused 
in  its  work  of  destruction  with  the  Hessian  fly.  In  Ohio,  at  a  time 
when  the  Hessian'  fly  was  being  accused  of  devastating  whole  fields  of 
wheat  in  the  fall,  by  collecting  a  great  number  of  the  affected  plants 
at  the  beginning  of  winter  and  placing  them  in  the  insectary  I  reared 
fully  as  many  of  these  as  I  did  of  the  Hessian  fly,  which  at  that  time  I 
was  especially  engaged  in  investigating.  It  is  on  this  account  that  the 
entomologist  who  attempts  to  study  the  economics  of  the  Hessian  fly, 
which  does  not  breed  in  the  grasses,  will  find  the  greatest  difficulty  in 
weighing  the  evidence  offered  by  those  who  can  not  or  will  not  note 
the  difference  in  the  nature  of  these  insects  and  the  great  similarity  in 
the  final  effects  of  their  attacks  upon  growing  fall  wheat  in  autumn 
and  spring. 

SELECTION    OF    FOOD   PLANTS    BY    THE    ADULTS. 

Either  some  varieties  of  the  same  kind  of  grain  are  more  or  less 
repugnant  to  the  flies,  or  else  they  possess  a  very  finely  adjusted  sense 
of  the  larval  preferences  for  certain  other  varieties,  for  they  certainly 
exhibit  a  considerable  discrimination  in  their  selection  of  the  different 
varieties  of  wheat  on  which  to  place  their  eggs.  Doctor  Forbes  has  called 
attention  to  the  fact  that  the  most  seriously  injured  fields  of  wheat  in 
Fulton  County,  111.,  in  1883,  were  of  the  Fultz  variety.  At  Lafayette, 
Ind.,  June  14,  1889,  among  a  lot  of  experiment  plats  on  the  experi- 
ment-station grounds,  sown  side  by  side,  on  the  same  day,  with  the 
same  soil  and  other  conditions,  there  was  a  marked  difference  between 
the  number  of  affected  straws  in  the  Velvet  Chaff  and  in  the  Michigan 
Amber,  the  infestation  being  fully  four  times  greater  in  the  former 
than  in  the  latter.  Even  in  the  case  of  larger  fields  bordering  each 
other  the  conditions  did  not  vary,  and  where  the*  two  varieties  over- 
lapped along  the  margins  the  same  partiality  for  the  Velvet  Chaff  had 
been  shown.  Doctor  Fletcher  has  also  noted  a  strong  prejudice  in  favor 
of  some  varieties  of  the  same  kinds  of  grasses.  For  instance,  while 
Poa  serotina  was  one  of  the  most  seriously  affected  of  all  of  the  grasses, 
P.  pratensis,  P.  caesia,  and  P.  compressa  were  almost  exempt  from 
attack.     Attack  on  Setaria  viridis  was  observed  in  a  single  instance. 

PLACE    AND    METHOD    OF    OVIPOSITION. 

According  to  Forbes,  the  eggs  are  placed  on  the  stems  of  grain,  "some 
being  pushed  down  beneath  the  ensheathing  bases  of  the  leaves  and 


49 

others  cemented  to  the  stems  just  at  the  margin  of  the  sheath,  while  still 
others  were  placed  along  the  edge  of  the  sheathing  base  of  the  leaf, 
sometimes  being  thrust  under  the  edge."  This  agrees  with  my  own 
observations  and  is  doubtless  the  usual  method  of  oviposition,  as  the 
main  object  on  the  part  of  the  female  is  to  place  the  eggs  where  the 
young  larvae  will  the  most  easily  reach  the  tender,  juicy  stem  as  soon 
as  possible  after  escaping  from  the  egg,  and  is  probably  true  in  the 
case  of  grasses  as  well  as  of  grain.     , 

METHOD    AND    NATURE    OF   ATTACK. 

Both  Doctor  Lintner  and  Doctor  Forbes  have  endeavored  to  indicate 
this  by  the  selection  of  explanatory  common  names  for  this  insect.  The 
former,  disregarding  Fitch's  name,  American  Meromyza,  as  too  tech- 
nical, and  having  observed  the  larvae  in  the  full-grown  straws  only, 
gave  it  the  name  of  the  ''wheat-stem  maggot,"  while  Doctor  Forbes, 
having  first  encountered  the  larva?  in  the  bulbous  lower  stem  in  early 
spring,  gave  it  the  name  of  the  "wheat-bulb  worm,''  on  account  of 
its  resemblance  to  the  "  wheat-bulb  maggot"  (Hylemyia  coarctata)  of 
England.  It  is  really  a  maggot  and  affects  the  stems  of  the  plants 
which  it  infests,  besides  being  the  largest  maggot  of  this  kind  at 
present  known  to  attack  the  stems  of  grain  in  this  manner  in  this 
country;  hence,  in  order  to  distinguish  it  from  other  smaller  stem 
maggots,  I  have  here  termed  it  the  "  larger  wheat  stem-maggot." 

The  larva  has  no  jaws  or  mouth,  but  a  couple  of  hook-shaped 
appendages  by  which  it  tears  the  plant  and  feeds  from  the  juices,  the 
cavity  made  hy  this  destruction  of  the  stem  being  filled  by  a  pomace- 
like mass  in  which  the  larva  is  to  be  found.  The  effect  on  the  plant 
is  shown  by  the  accompanying  illustration  (fig.  14,  d).  In  young 
plants  the  central  spindle-shaped  enfolded  leaf  is  killed,  precisely  as 
with  attacks  of  Oscinis  larvae,  the  detached  portion  turning  first  yellow 
and  later  brown,  then  shriveling  up  and  dying,  leaving  the  outer 
dower  leaves  uninjured.  In  Hessian -fly  attacks  this  spindle-shaped 
leaf  is  absorbed  and  does  not  appear  at  all  in  young  wheat  in  autumn, 
so  that  there  need  never  be  any  confusion  of  the  work  of  these  two 
insects  in  fall  wheat,  and  the  effect  on  the  full-grown  straws  is  even 
more  easily  distinguishable.  When  attacked  by  the  maggots  of  this 
species  the  i\x\\j  grown  straw  withers  at  the  upper  joint  and  all  that 
portion  of  the  stem  including  the  head,  the  sheath  excepted,  changes 
to  a  whitish  color,  the  remainder  of  the  plant,  including  the  upper 
sheath,  continuing  uninjured  and  of  the  usual  green  color.  The  Hes- 
sian fly  never  affects  the  full-grown  straws  in  this  manner  and  the 
lesser  wheat  stem-maggot  does  so  but  rarely,  so  that  the  presence  of 
these  maggots  in  the  straw  can  be  easily  detected  shortly  prior  to 
harvest  by  their  whitened  color  from  the  upper  joint  upward.  The 
larva?  are  within  the  stem  and  not  outside  and  under  the  sheath,  as 


50 

with  the  Hessian  fly;  they  are  larger  and  of  a  more  glassy  green  color 
than  those  of  the  lesser  wheat  stem-maggot,  and  it  is  only  when  still 
very  young  that  the  ordinary  farmer  need  ever  mistake  them  for  any 
of  the  others  mentioned  in  this  bulletin.  It  is  only  in  the  manner  of 
killing  the  stem  of  young  wheat  that  it  need  be  confused  with  others. 

EXTENT    OF   RAVAGES. 

Though  present  in  the  fields  every  year,  as  is  witnessed  by  the 
whitened  heads  of  grain  in  the  fields  just  prior  to  harvest,  I  have  never 
known  a  serious  attack  at  that  season  of  the  year;  nor  is  there  any- 
thing at  present  to  indicate  that  it  is  likely,  to  work  more  serious 
injury  at  this  season  in  the  future  than  it  has  in  the  past. 

Its  ravages  in  the  young  wheat  in  fall  and  spring,  as  illustrated  by 
the  outbreak  in  Illinois  in  1882-83,  are  not  as  yet  of  usual  occurrence, 
though  several  similar  instances  have  come  to  my  knowledge  within 
the  last  twenty  years.  In  two  cases — one  in  Indiana  in  1888  and 
another  in  Ohio  in  1900 — the  fields  Were  also  badly  infested  by  Hes- 
sian fly,  but  from  the  material  reared  it  would  seem  that  this  species 
was  to  be  credited  with  no  small  percentage  of  the  loss.  Occasionally 
fields  of  fall  wheat,  especially  if  sown  early,  are  attacked  in  the  fall 
and  ruined  by  this  insect  alone,  though  the  damage  is  in  some  cases 
attributed  to  the  Hessian  fly.  It  is,  however,  easy  enough  to  detect 
the  difference  between  injuries  caused  by  these  insects,  as  has  been 
explained  under  methods  of  attack. 

PREVENTIVE   MEASURES. 

The  liability  of  attack  from  this  insect  is  not  sufficiently  great  to 
warrant  any  expensive  measures  being  put  forth  in  order  to  forestall 
possible  outbreaks.  As  yet,  we  have  no  way  of  foretelling  these  sud- 
den attacks,  as  the  pest  has  never  proven  excessively  abundant  in  the 
same  locality  two  years  in  succession.  The  fact  that  late-sown  wheat 
is  less  subject  to  injury,  and  in  cases  where  the  two  have  been  found* 
in  a  combined  attack,  the  grain  has  been  sown  early,  indicates  that  this 
now-accepted  method  of  warding  off  an  attack  of  Hessian  fly  will  work 
equally  well  with  this  species.  There  is  nothing  at  present  to  indicate 
any  change  from  these  conditions  throughout  the  winter-wheat  grow- 
ing regions  of  the  Northern  States.  Whether  or  not  the  same  rule 
will  apply  in  the  South  remains  to  be  seen,  as  we  know  too  little  of 
the  pest  in  that  portion  of  the  country  to  be  able  to  speak  positively. 
In  the  North,  in  the  regions  devoted  to  the  raising  of  spring  wheat,  it 
would  appear  that  a  burning  over  of  the  grass  lands  in  winter  would 
reduce  the  probabilities  of  attack.  The  destruction  of  volunteer  wheat, 
which  should  be  done  in  any  case  as  a  protective  measure  against 
attacks  of  Hessian  fly,  will  of  course  tend  to  reduce  the  probability  of 
the  young  wheat  being  attacked  in  autumn.     It  must  be  borne  in  mind, 


51 

however,  that  this  is  a  grass  as  well  as  a  grain  insect,  and  eradication 
from  the  grain  fields  will  not  protect  from  infestation  from  without. 

NATURAL    ENEMIES. 

The  abundance  of  one  of  these  and  the  extent  to  which  they  are 
able  to  perform  their  deadly  work  is  a  most  encouraging  feature, 
viewed  from  the  standpoint  of  the  husbandman.  A  small,  shining 
black,  four-winged  fly,  with  reddish-yellow  legs  (Ccelinius  meromyzde 
Forbes),  is  exceeding  beneficial  in  its  parasitic  work  on  the  maggots  of 
this  pest.  This  parasite  was  discovered  and  described  by  Doctor 
Forbes  in  connection  with  the  investigations  of  the  outbreak  in  Illinois 
in  1883.  So  abundant  is  this  parasite  that  it  is  almost  impossible  to  rear 
the  flies  from  the  straws  in  July  without  also  rearing  numbers  of  these 
diminutive  friends.  They  attack  the  maggots  by  placing  their  Qgg^  in 
their  bodies,  and  the  eggs  hatching  feed  upon  the  maggots  and  destroy 
them.  This  parasite  occurs  generally  with  the  depredator,  even  in 
the  far  North. 

Another  natural  enemy  is  the  mite  Pedicidoides  (Heteropus)  ventri- 
cosus  NewTport,  illustrated  on  page  22.  The  }Toung  of  this  insect  are 
so  very  minute  as  to  be  quite  invisible  to  the  unaided  eye.  They  are 
without  wings,  but  very  active,  and  make  their  wa}T  to  the  maggot 
working  within  the  stem  and  fastening  themselves  upon  it  suck  its 
blood,  in  the  meantime  themselves  increasing  rapidly  in  size  until 
the}r  appear  like  minute  globular  eggs,  the  abdomen  being  distended 
with  young,  as  there  are  no  males,  and  the  body  having  much  the 
proportions  the  stem  has  to  the  pumpkin.  Each  female  gives  birth 
to  a  great  number  of  young,  which  at  once  either  escape  to  other  stems 
to  hunt  out  their  victims  or  else  settle  down  with  the  parent.  These 
are  frequently  found  attacking  the  maggots  and  are  apt  to  escape 
detection,  or,  if  observed,  mistaken  for  eggs.  The  reference  in  the 
Prairie  Farmer,  calling  attention  to  the  presence  of  what  probably 
were  these  maggots  in  stems  of  wheat  previously  cited,  also  mentioned 
the  presence  of  nine  eggs  with  the  maggot.  Without  a  doubt  these 
were  the  mites  that  had  attacked  the  maggot,  though  this  was  long 
before  the  mite  was  known  to  inhabit  this  Country,  it  being  a  native 
of  Europe,  as  far  as  now  known. 

THE  LESSER  WHEAT  STEM-MAGGOT. 

( Oscinis  carbonaria  Loew.     Fig.  15,  (/. ) 

With  our  present  knowledge  of  the  early  stages  of  development  it 
is  yet  impossible  for  me  to  separate  out  from  several  other  allied 
species  such  as  belong  to  this  one  and  give  a  detailed  account  of  its 
life  cycle,  and  especially  is  this  true  with  reference  to  Oscinis  soror, 
or  what  is  the  same  thing,  Oscinis  variabilis  Loew.  To  be  able  to  do 
this  will  require  the  most  careful  and  exact  studies  of  the  early  stages 


52 

of  the  offspring  of  adult  flies  belonging  to  each  species  ovipositing  on 
plants  known  of  a  certainty  to  be  free  from  infestation  by  other 
species.  Such  studies  can  only  be  carried  out  with  the  aid  of  better 
conveniences  than  I  have  had  at  my  disposal,  and  should  be  taken  up 
by  the  General  Government,  whose  investigators  are  not  restricted  by 
State  lines,  and -who  can  follow  wherever  their  problems  may  lead  them. 
Though  Oscinis  soror  ( 0.  variabilis)  has  been  reared  from  growing 
wheat  b}^  others  as  well  as  myself,  I  have  found  that  O.  carbonaria 
has  been  thus  obtained  with  the  greatest  frequency  over  the  widest 
range  and  under  conditions  that  lead  to  the  belief  that  it  is  the  more 
important  of  the  two,  from  an  economic  point  of  view  at  least. 

LIFE   HISTORY. 

This  can  only  be  given  in  a  general  way,  as  in  no  instance  has  the 
progeny  of  a  single  female  been  carried  through  the  life  cycle  and  the 
several  broods  throughout  the  year  clearly  denned.     I  have  myself 

reared  this  species  from 
growing  wheat  in  Illinois, 
Indiana,  and  Ohio,  over  not 
to  exceed  two  degrees  of  lat- 
itude, or  collected  them  in 
the  wheat  fields  throughout 
this  area,  or  they  have  been 
reared  in  Washington  in  the 
Department   insectary  from 

Fig.  15.— Oscinis  soror  Macq.;  a,  mature  fly:  b,  antenna  plants  Sent  there  by  me  irom 
of  same;  c,  puparium;  d,  head  of  0.  carbonaria— a,  c,  d,  £q]q  game  territorv  as  f  ol_ 
magnifled;  b,  still  more  enlarged  (original).  ,  ' 

lows:  Urbana,  111.,  July, 
August,  and  September;  Oxford,  Ind. ,  from  May  to  October,  not  inclu- 
sive; Lafayette,  Ind.,  July,  August,  and  September;  Wooster,  Ohio, 
May,  June,  July,  August,  and  September;  and  in  the  latter  locality 
from  August-sown  wheat.  In  the  insectary  I  have  also  reared  it  in 
November,  December,  and  the  following  April,  but  did  not  observe  it 
abroad  in  that  locality  during  November,  December,  or  April.  Besides 
these  rearings  of  mine,  it  was  reared  at  Washington,  July  7,  from  plants 
received  on  the  3d  of  same  month  from  Prof.  Lawrence  Bruner, 
West  Point,  Nebr.,  and  reared  by  Forbes,  in  Illinois,  September  17, 
from  volunteer  wheat.  This  is  the  species  mentioned  by  Doctor 
Fletcher  as  being  so  destructive  in  the  Dominion  of  Canada  in  1890,  as 
shown  by  specimens  of  the  adult  which  he  has  kindly  sent  me.  a 

There  was  a  bad  outbreak  of  this  insect  in  a  field  of  wheat  near 
Wooster,  Ohio,  in  the  fall  of  1891,  and  the  field  was  badly  affected. 
In  March  of  the  following  year  I  found  many  larvae  and  pupse  about 
the  bases  of  the  affected  plants,  and  an  attempt  was  made  to  study 

a  See  Experimental  Farm  Reports,  1890,  p.  158,  and  1898,  p.  177. 


53 

them  further,  but  insufficient  facilities  for  doing  so  prevented.  There 
was,  however,  plenty  of  evidence  that  the  insect  may  winter  in  either 
the  larval  or  pupal  stages.  A  single  specimen  was  reared  at  the 
Department  in  Washington  from  a  stalk  of  wheat  received  from  Mr. 
J.  (Jr.  Kingsbury,  editor  of  the  Indiana  Farmer,  the  fly  appearing 
June  18.  In  this  case  the  maggot  was  in  the  straw  above  the  upper 
joint,  and  the  wheat  head  was  evidently  killed  by  its  attack.  From  all 
of  these  facts  it  seems  that  its  life  cycle  may  be  about  as  follows:  It  may 
winter  over  in  the  lield  either  in  the  larval  or  pupal  stage,  the  adults 
emerging  in  May.  From  the  presence  of  larvae  in  the  stems  of  wheat 
and  grass  from  which  adults  have  afterwards  been  reared  it  would 
appear  that  there  is  a  brood  of  flies  emerging  in  June  and  July,  much 
as  in  Meromyza  americana^  which  lay  their  egg^  in  grass  and  volunteer 
grain;  another  brood  of  flies  resulting  in  September  and  October 
whose  offspring  hibernate  as  previously  stated,  there  being,  as  in 
Meromyza,  three  broods  each  year,  from  six  weeks  to  two  months  being 
required  for  the  insect  to  pass  through  its  development  during  the 
summer  months. 

FOOD    PLANTS. 

1  have  reared  these  flies  only  from  wheat,  probably  because  I  have 
made  no  special  effort  to  rear  them  from  any  other  plant.  Doctor 
Fletcher  has  reared  the  species  from  Agropyron  caninum,  A.  lenerum, 
A.  repens,  Poa  pratensis,  and  Ely  mux  canadensis.*1 

fr 

PLACE    AND    METHOD    OF    OVIPOSITION. 

I  have  observed  oviposition  only  among  small  wheat  plants,  but 
presume  that  the  methods  employed  in  such  cases  do  not  differ  from 
those  where  the  food  plant  is  some  of  the  grasses.  The  object  on  the 
part  of  the  female  seems  to  be  to  place  her  eggs  low  down  on  the  plant, 
as  near  the  root  as  possible  and  along  the  enveloping  edge  of  the 
sheath.  The  very  young  larva1  are  always  to  be  found  in  this  situa- 
tion, and  the  edges  of  the  enveloping  bases  of  the  leaves  are  always 
ragged  and  discolored  in  infested  plants. 

NATURE    OF   THE    INJURY. 

The  young  maggot  on  hatching  from  the  egg  feeds  along  the  thin 
edge  of  the  lower  base  of  the  enfolding  leaf  where  it  is  white,  juicy, 
and  tender.  It  seems  to  make  no  effort  at  first  to  reach  the  central 
portion  of  the  plant,  seeming  to  know  that  that  part  will  remain  ten- 
der and  succulent,  but  gradually  works  its  way  inward  and  upward  to 
a  point  just  below  where  the  central  spindle-shaped  unfolding  leaf 
leaves  the  ensheathing  portion  of  the  next  older  one,  the  exact  locality 
seeming  to  be  decided  upon  according  to  the  toughness  of  this  central 

o  Experimental  Farms  Reports,  1890,  p.  158. 


54 

leaf,  which  of  course  varies  with  age  and  ma}7  be  the  first  slender  shoot 
of  the  plant,  or  one  of  the  older  and  tougher  tillers  of  much  older 
plants.  This  central  compactly  rolled  leaf  is  cut  off,  the  maggot  at 
first  working  upward  until  this  leaf  becomes  too  tough  or  begins  to 
wither,  when  it  reverses  its  position  and  works  downward,  where  the 
food  suppl}7  is  always  fresh  and  juicy.  Pupation  does  not  take  place 
here,  but  the  larva  makes  its  way  when  full  fed  to  between  the  bases 
of  the  older  leaves,  and  in  that  situation  the  puparia  are  to  be  found. 
A  very  young  plant  does  not  admit  of  very  extended  travel  by  the 
larva,  and  in  an  older  one  the  continuity  of  its  path  is  soon  obliterated 
by  the  growth  of  the  plant  itself,  and  the  larva  is  frequently  found  a 
couple  of  inches  above  the  base  where  it  entered  after  hatching  from 
the  egg^  as  is  witnessed  by  the  minute  patches  eaten  out  of  the  leaf. 
As  but  a  single  maggot  is  found  in  each  stem,  I  have  often  wondered 
if  the  female  so  distributed  her  eggs  as  to  prevent  a  clashing  of  young, 
and  feel  very  much  inclined  to  the  opinion  expressed  in  some  unpub- 
lished notes  by  Mr.  Pergande  to  the  effect  that  more  than  one  egg  may 
be  deposited  about  a  single  stem,  but  the  oldest  and  strongest  maggot 
kills  off  the  weaker,  leaving  but  one  in  full  possession. 

EXTENT    OF   RAVAGES. 

Usually  the  work  of  this  species  is  so  confused  with  that  of  others 
as  to  render  anything  like  a  definite  estimate  of  the  damage  that  can 
be  justly  charged  to  its  attacks  in  the  grain  fields  almost  impossible. 
I  have  never  observed  injuries  to  the  full-grown  straw,  though  I  have 
occasionally  found  larvse  in  them  that  I  presumed  to  belong  to  this 
species.  In  fall  wheat  the  plant  recovers  from  a  slight  injury,  espe- 
cially if  growing  in  a  fertile  soil,  and  I  apprehend  that  more  damage 
will  follow  an  attack  in  fields  where  the  soil  is  poor  or  badly  worn 
than  where  it  is  richer.  In  the  field  of  wheat  near  Wooster,  Ohio, 
that  was  so  severely  injured  in  1891,  the  Hessian  fly  was  also  present 
and  did  fully  as  much  injury  as  this  insect,  both  I  should  say,  destroy- 
ing fully  one-half  the  crop.  Dr.  Fletcher  has  called  attention  to  a 
field  of  spring  wheat  in  Canada  that  was  damaged  fully  75  per  cent, 
for  the  most  part  due  to  the  attacks  of  this  species.  In  the  United 
States,  I  do  not  believe  that  an  injury  of  from  5  to  15  per  cent  of  the 
crop  by  reason  of  the  attacks  of  this  and  other  Oscinis  is  at  all  unusual, 
but  this  can  not  in  all  cases  be  wholly  charged  up  to  this  particular 
species. 

DESCRIPTION. 

The  following  description  of  the  fly  of  Oscinis  carbonaria  has  been 
kindly  drawTn  up  for  me  by  Mr.  Coquillet: 

A  small,  black,  two- winged  fly  having  the  knobs  of  the  halteres,  the  feet,  and 
usually  both  ends  of  the  tibiae  yellow.     Length  varying  from  1  to  nearly  2  milli- 


55 

meters  (from  one  twenty-fifth  to  nearly  one-twelfth  of  an  inch).  The  last  joint 
of  the  antenme  is  nearly  circular  in  outline,  and  on  the  upper  edge  is  a  nearly  bare 
bristle  or  arista;  on  the  upper  part  of  the  otherwise  opaque  head  is  a  polished, 
nearly  triangular  spot  that  extends  from  the^extreme  vertex  almost  to  the  antenna?. 
The  wings  are  nearly  transparent  and  are  without  an  auxiliary  vein — that  is,  there 
are  only  three  (instead  of  four)  veins  that  terminate  in  the  front  edge  of  the  wing 
before  its  apex;  the  vein  bordering  the  front  edge  of  the  wing  extends  beyond  the 
extreme  apex  of  the  wing;  the  usual  two  small  cells  near  the  base  of  the  wing  are 
wanting,  the  anterior  one  being  confluent  with  the  discal  or  central  cell,  while  the 
posterior  one  is  wanting,  there  being  only  one  cell  (the  axillary)  behind  the  fifth 
vein.  The  legs  are  devoid  of  bristles  and  of  stout,  apical  spurs,  and  are  rather  short 
and  robust;  the  first  joint  of  the  feet  is  rather  slender  and  longer  than  any  of  the 
other  joints.  The  thorax  is  also  without  bristles,  except  along  the  sides  and  across 
the  posterior  end;  it  is  somewhat  polished  and  is  devoid  of  gray  dust.  The  face 
does  not  project  strongly  forward  on  its  lower  part;  the  proboscis  is  short,  robust, 
and  terminates  in  the  fleshy  lips. 

CLOSE    RESEMBLANCE   TO   OSCINIS   SOROR   MACQ. 

Oscinis  soror  Macq.  is  very  closely  related,  but  ma}T  be  distinguished 
by  the  fact  that  the  polished  spot  on  the  upper  part  of  the  head 
extends  only  about  halfway  from  the  vertex  to  the  antennae,  instead 
of  almost  reaching  the  antennae,  as  in  the  preceding  species.  (D.  W. 
Coquillett. ) 

At  present,  owing  to  the  confusion  of  this  species  with  soror^  an 
account  of  which  will  follow,  it  seems  impossible  to  give  desirable 
descriptions  of  the  preparatory  stages  of  this  insect.  I  have  followed 
those  of  Professor  Garman,  not  knowing  whether  he  was  dealing  with 
this  species  or  not,  but  because  his  descriptions  seem  to  me  to  apply 
as  well  to  this  as  any  that  I  could  supply.  It  must  be  kept  in  mind, 
however,  that  this  is  only  a  temporary  makeshift  to  give  some  kind  of 
an  idea  of  what  these  look  like,  and  thus  enable  the  farmer  to  reduce 
the  uncertainty  as  to  the  identical  species  that  is  injuring  his  crop, 
and  that  later  and  more  careful  investigations  will  probably  show  that 
this  and  several  other  species,  but  with  habits  that  are  practically  the 
same,  have  been  confused,  and  thus  the  present  arrangement  serve  a 
practical  if  not  a  scientific  purpose. 

Egg. — The  egg  of  what  is  supposed  to  be  this  species  was  described  by  Mr.  Per- 
gande  in  the  Department  notes  as  follows:  Colorless,  polished,  and  longitudinally 
ribbed  wTith  numerous  extremely  fine  transverse  striae. 

Larva. — Cylindrical,  white,  with  faint  yellow  cast.  Body  composed  of  thirteen 
segments.  No  head  and  no  legs.  Mouth  with  two  strong  black  hooks.  Posterior 
segment  of  body  with  a  pair  of  knob-like  prominences.  Length  of  alcoholic  speci- 
mens, 0.14  inch. 

Pupa. — In  this  stage  the  insect  is  inclosed  in  the  hardened  and  brown  skin  of  the 
larva  and  this  is  called  the  puparium.  This  last  is  bright  yellowish-brown,  with 
distinct  and  very  finely  wrinkled  divisions.  The  two  knob-like  prominences  in  the 
larva  are  retained  and  are  conspicuous  at  one  extremity.  The  black  hooks  of  the 
larva  are  molted  with  the  skin  and  can  be  seen  through  the  puparium.  The  obso- 
lete mouth  of  the  larva  is  withdrawn,  blackened,  and  wrinkled.  Length  from  0. 10 
to  0.14  inch. 


56 

PREVENTIVE   MEASURES. 

It  is  doubtful  if  one  farmer  out  of  a  thousand  fully  realizes  the 
danger  arising-  from  volunteer  wheat.  This  growth  springs  up  in  the 
fields  in  greater  or  less  abundance,  and  is  almost  invariably  left  to 
itself,  as,  having  no  value,  it  is  thought  not  worth  while  to  bother 
with  it.  Besides,  the  general  practice  in  many  sections  of  the  coun- 
try of  seeding  the  wheat  lands  to  timothy  and  clover  would  prevent 
any  attempt  to  destroy  the  volunteer  wheat,  except  by  pasturing, 
which  is  not  considered  a  part  of  good  husbandry  at  that  season.  A 
rotation  of  crop,  however,  has  in  itself  some  advantages,  as  it  forces 
the  flies  to  migrate  from  one  field  to  another,  in  which  there  must  be 
more  or  less  casualties,  and  many  more  would  probably  be  attracted 
to  the  grasses  and  the  young  fall  wheat  be  protected  to  this  extent 
from  attack.  Where  wheat  is  to  follow  wheat  in  the  same  field,  it 
will  certainly  pay  the  farmer  to  destroy  this  volunteer  growth,  as  it 
not  only  harbors  all  of  these  flies  and  offers  unusual  advantages  for 
the  development  of  this  midsummer  brood,  but  it  offers  a  breeding 
place  for  the  Hessian  fly  as  well.  Volunteer  wheat,  then,  should  be 
destroyed  wherever  possible  by  the  plow  or  disk  harrow,  and,  where 
practicable,  by  pasturing,  so  as  to  prevent  the  flies  from  breeding 
therein.  Burning  over  the  grass  lands,  except  timothy  or  clover, 
where  it  is  probably  not  necessary,  will  offer  much  protection,  espe- 
cially in  spring-wheat  growing  regions,  and  where  fall  wheat  is  much 
grown,  reasonably  late  sowing  will  probably  prove  one  of  the  most 
effective  means  of  protection. 

NATURAL   ENEMIES. 

While  this  species  probably  has  its  usual  number  of  natural  ene- 
mies, it  is  not  always  possible  to  determine  the  exact  species  from 
which  these  have  been  reared,  but  an  insect  that  is  parasitic  on  one 
species  of  these  flies  might  be  confidently  looked  for  as  being  parasitic 
upon  other  allied  species.  Bhyssalus  oscinidis  Ashm.  is  parasitic  on 
a  species  of  Oscinis  larvae  mining  in  the  leaves  of  plantain,  in  Wash- 
ington, D.  C.  Apliaereta  californica  Ashm.  and  A.  oscinidis  Ashm. 
have  both  been  reared  from  other  species  of  Oscinis,  while  I  have 
reared  Cyrtogaster  occidentalis  Ashm.  from  either  this  species,  0. 
soror,  or  0.  wnbrosa,  in  Indiana,  though  it  is  known  to  occur  from 
Texas  to  South  Dakota  and  east  to  Virginia  and  the  District  of  Colum- 
bia. These  are  all  minute  four- winged  flies,  and  there  are  probably 
many  others  that  also  help  to  keep  these  flies  reduced  in  numbers.  I 
have  also  observed  the  common  parasitic  fungus  Entomophthora  m.uscm. 
attacking  the  flies,  but  this  is  probably  a  minor  factor  among  their 
natural  enemies. 


57 

THE  AMERICAN  FRIT-FLY. 

( Oscinis  soror  Macq.     Fig.  15,  p.  52.) 

This  species  has  been  so  interminably  confused  with  other  allied 
species,  especially  with  what  has  been  going  the  rounds  as  Oscinis 
varabilis  Loew?  a  synonym,  and  as  frequently  confused  with  0.  car- 
bonaria  as  with  this,  that  it  seems  almost  impossible  to  say  anything 
about  it  with  any  degree  of  certainty  that  one  is  not  really  dealing 
with  something  else.  Oscinis  soror  is,  nevertheless,  a  valid  species, 
and  its  larvae  in  all  probability  attack  growing  grain,  though  I  have 
myself  rarely  reared  it  from  grain,  and  my  proof  of  its  destructive- 
ness  in  wheat  fields  is  unfortunately  not  as  conclusive  as  1  wish  it  were. 
The  larvae  certainly  have  a  wide  range  of  food  plants,  as  I  have  reared 
it  from  maggots  in  the  stems  of  Panicym  crus-galli  in  Indiana  during 
September,  and  also  from  the  stems  of  Poapratensis  in  June  and  from 
wheat  in  July.  It  has  also  been  reared  from  larvae  wintering  in  the 
seed  capsules  of  Yernonia  noveboracensis  May  15  in  Washington,  D.  C. ; 
in  June  and  July,  at  Columbus,  Ohio,  from  oat  plants;  from  the  roots 
of  cucumber,  October  2,  in  Maryland;  and  from  strawberry  plants  in 
Michigan.  Last  year  I  reared  the  flies  from  the  stems  of  Eragrostis 
minor  at  Urbana,  111.,  in  September.  These  definitely  authenticated 
rearings  of  the  flies  show  a  wide  range  of  food  plants,  and  the  species 
is  one  of  the  most  abundant  of  all  the  Oscinids. 

CONFUSION    WITH    OTHER    SPECIES. 

Owing  to  a  species  having  been  found  in  Illinois  and  Kentucky 
attacking  wheat  and  doubtfully  determined  by  Doctor  Williston  as 
Oscinis  variabilis  Loew,  now  known  to  be  a  synonym  of  this  species, 
and  this  determination  having  been  applied  elsewhere  to  other  Oscinidae 
attacking  wheat,  has  led  to  much  confusion,  as  where  the  name  O.  vari- 
abilis has  been  applied  to  a  form  committing  depredations,. we  can  not 
say  with  any  degree  of  certainty  whether  the  insect  involved  was  this 
species  or  0.  carbonaria,  unless  specimens  actually  reared  from  the 
plants  so  attacked  are  at  hand.  Realizing  the  difficulty  when  I  began 
the  preparation  of  this  bulletin,  I  applied  to  Mr.  Coquillett,  of  the 
United  States  National  Museum,  for  suggestions  as  how  to  best  over- 
come it  and  received  from  him  an  offer  to  determine  any  material 
reared  from  larvae  attacking  wheat  in  various  parts  of  the  country. 
Doctor  Fletcher  had  published  accounts  of  the  ravages  of  Oscinis  vari- 
abilis Loew?  in  Canada,  Dr.  Otto  Lugger  of  similar  ravages  of  Oscinis 
soror  in  Minnesota,  and  Professor  Garman  of  the  attacks  of  Oscinis 
variabilis  Loew?  in  Kentuck}r.  Application  was  therefore  made  to 
Doctor  Fletcher,  Professor  Washburn,  successor  to  the  late  Doctor 
Lugger  in  Minnesota,  and  Professor  Garman,  for  reared  material  in 
order  to  as  far  as  possible  place  the  responsibility  for  these  depredations 


on  the  species  actually  engaged  therein.  Material  kindly  placed  at  my 
disposal  by  Doctor  Fletcher  has  shown  that  it  was  Oscinis  carbonaria 
Loew  that  committed  the  depredations  in  Canada.  Professor  Washburn 
was  less  fortunate,  though  he  did  all  that  was  possible  for  him  to  do  to 
aid  me,  and  sent  specimens  that,  judging  from  the  labels  attached,  had 
been  reared,  by  Doctor  Lugger,  but  whether  from  wheat  or  not  it  is 
impossible  to  determine,  as  nothing  could  be  found  that  would  throw 
any  light  upon  this  point.  The  specimens  sent  me  from  Minnesota  by 
Professor  Washburn  comprised  two  species,  0.  soror  and  0.  dm^sata 
Loew,  the  former  having  been  supposed  by  Doctor  Lugger  to  have  been 
responsible  for  the  injuries  to  wheat  in  Minnesota  in  1892,  while  the 
latter  was  reared  by  me  from  wheat  plants  in  Ohio  in  the  fall  of  1897, 
thus  indicating  that  both  might  have  been  involved  in  the  Minnesota 
trouble.  Assuming  that  Doctor  Lugger  had  sufficient  grounds  for 
holding  Oscinis  soror  responsible  for  the  damage  in  his  State  at  the 
time  stated,  I  have  so  considered  it  here,  but  have  thought  proper  to 
indicate  the  uncertainties  surrounding  this  conclusion.  Not  being  able 
to  secure  any  material  whatever  from  Professor  Garman,  I  am  forced 
to  reluctantly  place  the  blame  for  the  outbreak  in  the  wheat  fields  in 
Kentucky  in  1889  upon  Oscinis  soror,  but  with  a  strong  suspicion  that 
it  was  really  Oscinis  carbonaria  that  was  responsible  for  the  trouble. 
I  have  applied  Doctor  Lugger's '  descriptions  of  the  larva  and  pupa  to 
this  species  as  being  the  best  that  can  be  done  with  our  present  knowl- 
edge of  these  insects,  but  subject  to  revision,  as  future  investigations 
shall  clear  up  more  or  less  of  the  obscurity  at  present  surrounding 
them. 

DEPREDATIONS   IN   MINNESOTA. 

There  is  one  fact  connected  with  the  Oscinis  problem  in  Minnesota 
that  seems  to  point  especially  to  0.  soror  as  the  real  depredator,  and 
not  0.  dorsata,  and  that  is  in  the  striking  difference  in  the  color  of 
the  two,  the  former  being  black  and  the  latter  yellow,  a  difference 
that  could  hardly  have  escaped  the  keen  eyes  of  Doctor  Lugger,  and  I 
can  not  but  feel  that  he  was  correct  in  his  attributing  the  depredations 
to  the  species  now  being  considered.  I  strongly  suspect  that  some  of 
the  4 '  deadheads "  to  which  Doctor  Fletcher  has  called  attention  in  his 
reports  and  other  publications  as  occurring  in  the  wheat  fields  of  Mani- 
toba and  the  Northwest  Territories  may  have  been  to  some,  extent  due 
to  the  work  of  this  species  also. 

Doctor  Lugger  seems  not  to  have  studied  the  several  generations  of 
the  species  in  his  State  (Minnesota),  but  gave  his  attention  especially 
to  the  one  that  proved  the  most  destructive.  From  what  has  been 
stated  of  the  insect  farther  to  the  southward,  it  would  appear  that 
there  are  the  same  number  of  broods  as  with  O.  carbonaria,  the  pest 
wintering  over  in  the  young  plants  of  fall  wheat  and  grass.  In  Min- 
nesota it  evidently  winters  in  the  straw,  from  which  it  would  seem 


59 

that  in  the  north  there  is  one  less  brood  than  there  is  farther  to 
the  south,  a  condition  of  affairs  entirely  possible,  as  we  now  know 
that  the  Hessian  fly  is  there  largely  at  least  single  brooded,  but  double 
brooded  farther  south.  In  his  second  annual  report  as  State  ento- 
mologist, pages  6  to  10,  Doctor  Lugger  gives  these  facts  relative  to 
the  work  of  the  insect  in  his  State: 

During  the  summer  and  early  part  of  the  fall  numerous  letters  were  received  from 
many  parts  of  the  State  in  which  the  writers  complained  about  minute  worms  which 
infested  the  stems  of  wheat  just  above  a  joint  from  3  to  4  inches  above  the  ground. 
The  specimens  received  at  the  same  time  showed  that,  as  a  general  rule,  the  first 
and  second  joints  of  the  plant  were  infested.  Some  farmers  complained  that  their 
crop  of  wrheat  was  thus  very  materially  reduced.  The  plants  harboring  the  worms 
did  not  indicate  their  presence  until  flowering  time,  but  as  soon  as  the  head  began 
to  form  the  stem  above  the  injured  joint  wilted,  turned  yellowish,  and  soon  broke 
down  entirely  by  bending  over  the  infested  spot.  *  *  *  But  when  the  infested 
stems  were  investigated  it  was  found  that  the  wrorm  had  weakened  them  to  such  an 
extent  that  when  the  head  was  formed  the  plant  became  topheavy  and  broke  down 
at  the  weakest  point  from  force  of  gravity.  *  *  *  These  heads  were  either 
entirely  empty  or  filled  with  berries  more  or  less  shrunken.  The  bent  or  partly 
broken  stems  were,  as  a  general  rule,  still  adhering  to  the  lower  portion  of  the  plant. 
This  bending  or  breaking  had  taken  place  most  frequently  above  a  node  or  joint 
about  3  inches  from  the  ground.  Just  below  this  breakage,  and  immediately  above 
the  joint,  the  culprits  were  to  be  found.  In  most  cases  but  one  puparium,  but  in 
a  few  cases  two,  three,  or  even  more  puparia  could  be  detected.  Such  a  puparium 
is  the  contracted  and  hardened  skin  of  the  larva  or  wTorm;  it  is  of  a  glossy,  chestnut- 
brown  color,  shading  to  yellowish  brown  toward  the  smaller  end.  If  closely 
inspected  it  showTs  faint  traces  of  sutures  or  segments.  *  *  *  These  seed-like 
objects  contain  at  this  time  (October)  whitish  larvae  or  worms,  and  no  pupae  have 
been  detected  inside  of  them  up  to  this  date.  *  *  *  Judging  from  the  fact  that 
only  pupae  [puparia? — F.  M.  W.]  can  be  found  at  this  time,  it  would  appear  as  if 
this  insect  hibernates  in  that  stage.  This  is  really  the  only  one  in  which  it  could 
well  pass  our  northern  winters,  being  in  that  stage  well  protected  by  its  old  and 
thickened  skin  and  by  the  stem  of  the  plant.  The  puparia  are  inserted  in  the  mate- 
rial of  the  upper  part  of  the  node,  inaccessible  to  any  moisture  from  the  outside,  as 
the  stem  above  does  not  break  off  entirely,  but  simply  bends  in  a  more  or  less  acute 
angle  a  short  distance  over  them,  thus  preventing  the  entrance  of  water.  Yet  the 
culm  is  sufficiently  fractured  to  permit  a  free  exit  of  the  future  fly  in  spring.     *    *    * 

The  damage  caused  by  this  insect  in  1892  was  by  no  means  small.  In  many 
places  fully  one-fourth  of  the  entire  crop  of  wheat  was  destroyed,  and  in  a  great 
many  more  the  losses  amounted  to  at  least  one-tenth.  As  many  places  are  badly 
infested,  the  total  amount  is  quite  large,  and  if  no  steps  are  taken  to  prevent  it  a 
repetition  may  become  ruinous  in  1893.  Most  farmers  plowed  their  fields  in  the  fall 
of  1892  or  early  in  1893,  and  consequently  the  losses  in  the  latter  year  were  small, 
and  in  1894  but  very  few  of  these  insects  were  to  be  found.  The  spring  of  this  year 
[1896? — F.  M.  W.]  being  very  wet,  prevented  extensive  plowing,  and  the  insects, 
not  being  disturbed  or  plowed  under,  again  became  a  pest  and  caused  considerable 
damage.  The  name  "frit-fly"  is  a  well-deserved  one,  as  Swedish  farmers  call  the 
worthless  grain  resulting  from  the  attack  of  such  flies  "frits." 

LIFE    HISTORY. 

As  stated  by  Doctor  Lugger,  the  life  history  is  still  very  obscure,  and 
it  will  require  careful  study  and  close  observation  to  secure  a  knowledge 


60 

of  it  over  the  country.  The  facts  given  by  him  in  his  report  are  unlike 
what  has  been  observed  farther  south,  but  these  differences  are  not 
sufficient  to  indicate  that  it  was  not  this  species  that  caused  the  injuries 
mentioned.  Even  if  we  assume  that  the  insect  reared  in  Kentucky  by 
Professor  Garman  belonged  to  this  species,  we  find  that  adult  flies 
have  been  reared  by  others  in  May,  late  June,  and  early  July,  and 
again  in  September,  thereby  indicating  three  broods  in  the  vicinity  of 
latitude  40°,  the  species  wintering  as  larvae  or  pupae,  probably  the 
latter,  the  flies  emerging  from  these  ovipositing  in  May,  the  adults 
from  these  appearing  in  June  and  July,  these  in  turn  giving  origin  to 
a  fall  brood  in  September,  whose  progeny  winter  over  as  stated.  In 
more  northern  and  inland  sections  of  the  country  it  seems  that  the 
fall  brood  may  drop  out  and  the  one  occurring  farther  south  in 
midsummer  pass  the  winter  as  puparia  and  the  adults  emerge  the 
following  spring. 

FOOD   PLANTS. 

Either  this  has  a  greater  range  of  food  plants  than  Oscinis  carbo- 
naria,  or  else  we  have  not  learned  much  about  those  of  the  latter.  As 
it  is,  the  food  of  this  species  is  so  varied  as  to  almost  incline  one  to 
the  suspicion  that  it  stands  accused  of  ravages  that  should  be  placed 
to  the  credit  of  another  but  for  the  facts  supplied  by  Doctor  Lugger. 
However,  this  variation  in  its  bill  of  fare  gives  the  farmer  a  still 
better  opportunity  of  fighting  it  outside  his  grain  fields. 

DIFFICULTIES   IN   STUDYING   HABITS. 

The  fact  that  maggots  taken  from  wheat  plants  in  a  field  develop 
these  flies  does  not  necessarily  prove  that  other  maggots  attacking 
wheat  in  the  same  field  will  produce  the  same  species  of  flies;  there- 
fore, descriptions  drawn  up  from  such  collections  may  or  may  not  be 
correct,  and  for  the  same  reasons  observations  on  the  habits  of  such 
larvae  are  liable  to  be  incorrect.  It  is  only  by  placing  flies  on  plants 
known  to  be  free  from  all  other  infestation  and  studying  these  that  we 
shall  be  able  to  get  at  the  truth  in  relation  to  anatomical  and  biological 
facts.  An  investigator  will  then  know  just  which  species  he  is  dealing 
with,,  and  whatever  descriptions  are  drawn  up  from  material  secured 
in  this  manner  and  whatever  observations  are  made  upon  them  will  be 
sure  to  be  accurate  so  far  as  the  species  under  observation  is  concerned. 
In  no  case  has  this  been  done,  and  as  a  consequence  we  have  only  a 
general  knowledge  of  these  insects,  and  any  descriptions  of  the  larvae 
may  or  may  not  prove  correct  in  future.  Though  there  is  a  noticeable 
difference  between  the  adult  figured  by  Doctor  Lugger  as  this  species 
and  the  one  figured  by  Professor  Garman  as  Oscinis  variabilis  Loew  ? 
the  figures  of  the  larva  and  puparia  are  exceedingly  alike.  For  the 
same  reason  any  recommendations  looking  to  the  control  of  the  pest 


61 

in  the  grain  fields  must  be  made  somewhat  at  random  and  aimed  at 
Oscinida?  in  general  rather  than  at  this  particular  species. 

REMEDIAL   AND    PREVENTIVE    MEASURES. 

Over  the  area  where  winter  wheat  is  cultivated  the  same  measures 
that  have  been  urged  against  the  two  wheat  stem-maggots  will  apply 
equally  well  here,  so  far  as  we  now  understand  the  habits  of  this 
species.  These  are  the  destruction  of  volunteer  wheat,  the  burning 
over  of  waste  grass  lands  in  winter  and  early  spring,  and  late  sowing 
of  the  grain  in  fair*.  In  spring- wheat  regions  the  experience  of  Doctor 
Lugger  in  Minnesota  is  strongly  indicative  of  the  effect  of  plowing  the 
infested  fields  as  soon  as  possible  after  the  crop  has  been  removed. 
He  states  that  in  the  fall  of  1891  and  spring  of  1892  not  more  than 
one-half  of  the  acreage  of  wheat  land  was  plowed,  owing  to  unusually 
wet  weather  during  these  periods,  and  the  pest  that  had  gained  a  foot- 
hold, as  it  were,  in  1891,  meeting  with  no  reverses  on  account  of  lack 
of  plowing,  simply  continuing  to  increase  in  numbers,  with  the  result 
that  in  1892  it  committed  serious  and  widespread  depredations.  Where 
the  fields  can  be  burned  over  in  fall  or  spring  the  result  will,  of  course, 
be  the  extermination  of  the  pest  in  such  fields  in  the  northern  portions 
of  the  country,  but  farther  south  it  is  the  grass  lands  that  need  to  be 
burned  over,  since  there  is  no  way  of  reaching  the  insect  hibernating 
in  the  winter-wheat  plants.  The  fields  of  spring  wheat  in  the  North 
will,  of  course,  be  to  some  extent  also  protected  by  the  burning  over 
of  the  grass  lands  in  fall  or  spring. 

DESCRIPTION. 

The  difference  between  this  species  and  Osdnis  carbonaria  have 
already  been  pointed  out  in  the  treatment  of  the  latter  species  (see 
p.  55). 

Larva. — This  very  closely  resembles  that  of  O.  carbonaria,  as  is 
shown  by  the  illustrations  used  by  Doctor  Lugger  in  his  publications. 
He  states,  however,  that  the  larva  is  of  a  greenish-white  color  when 
alive  and  just  removed  from  the  culm. 

Pupariwn. — Here,  again,  it  would  be  difficult  to  identify  the  pupa- 
rium  by  either  the  illustration  or  description  given  by  Doctor  Lugger, 
as  both  closely  resemble  those  given  of  0.  variabilis?  by  Professor 
Garman.  Doctor  Lugger  describes  this  as  being  of  a  glossy  chestnut- 
brown  color,  shading  to  yellowish  brown  toward  the  smaller  end,  and 
showing  faint  traces  of  sutures  or  segments. 

Of  the  other  species  of  small  Oscinidre  whose  larvae  are  found  in  and 
about  the  stems  of  growing  grain  I  have  already  written,  and  it  is 
impossible  with  our  present  knowledge  of  them  to  go  into  further 
details.  Some  of  these  may  be  destructive  and  some  may  not,  as"  the 
fact  of  these  having  been  reared  from  grain  plants  does  not  necessarily 


62 

prove  that  they  are  destructive,  as  they  may  live  upon  the  dead  and 
decaying  older  leaves  or  they  may  simply  inhabit  the  burrows  made  by 
other  insects.  The  practical  farmer  will  probably  be  able  to  meet  their 
depredations  by  the  same  measures  that  have  been  recommended  for 
those  species  with  which  we  are  the  most  familiar,  at  least  until  a  more 
extended  study  can  be  made  and  more  light  thrown  on  their  habits. 

CONCLUSION. 

In  the  foregoing  it  has  been  the  aim  of  the  writer  to  so  present  this 
subject  as  to  enable  the  farmer  to  distinguish  some  of  the  more  obscure 
enemies  of  his  crops  and  prevent  a  peculiar  and  subtle  shrinkage  in 
the  profits  of  his  labors,  and  one  that  he  can  meet  in  most  cases  by 
simple  measures  that  cost  nothing  except  the  time  consumed  in  carry- 
ing them  out  during  seasons  or  days  of  comparative  inactivity  on  the 
farm.  Not  all  of  the  ravages  in  the  wheat  fields  are  due  to  the  Hessian 
fly,  and,  indeed,  the  crop  reports  are  usually  wholly  unreliable  in  respect 
to  the  actual  occurrence  of  this  insect,  except  it  be  in  cases  of  over- 
whelming numbers.  One  of  the  most  practical  preventive  measures 
that  can  be  applied  against  the  Hessian  fly  will  also  prove  of  value  in 
warring  against  these  other  pests,  viz,  late  seeding  of  fall  wheat  in 
autumn;  and  a  second  measure,  that  of  rotation  of  crops,  will  be  found 
almost  as  valuable.  Fighting  insects  demands  a  better  system  of 
farming,  which  of  itself  will  pay  in  other  directions,  and  the  American 
farmer  must  calculate  upon  insect  depredations  as  no  small  element  in 
his  business.  Of  what  use  is  it  to  rear  two  blades  of  grass  where  but 
one  grew  before  if  he  is  to  lose  both  of  them  by  reason  of  insect  attack? 
It  is  not  the  farm  but  the  profits  thereof  that  are  lost  through  the 
devastations  caused  by  injurious  insects,  and  it  costs  the  American 
farmer  more  to  feed  these  insidious  foes  than  it  does  to  educate  his 
children. 


UNIVERSITY  OF  FLORIDA 

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